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I ELLINOIS T UINS TI T
OF TECHNOLOGY
ITM 578 1
Security Technologies
Ray Trygstad
ITM 478/578
Spring 2004
Master of Information Technology & Management Program
CenterforProfessional Development
Slides based on Whitman, M. and Mattord, H., Principles of InformationSecurity; Thomson Course Technology 2003
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Learning Objectives:
Upon completion of this lesson the student
should be able to:
– Define and identify the various types of firewalls.
– Discuss the approaches to firewall
implementation.
– Discuss the approaches to dial-up access and
protection.
– Identify and describe the two categories of
intrusion detection systems.
– Discuss the two strategies behind intrusion
detection systems.
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Learning Objectives:
Upon completion of this lesson the student
should be able to:
– Discuss scanning, analysis tools, and content
filters.
– Understand trap and trace technologies.
– Discuss the process of encryption and define key
terms.
– Identify and discuss common approaches to
cryptography.
– Compare and contrast symmetric and asymmetric
encryption.
– Discuss various approaches to biometric access
control.
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Introduction
 Information security: a discipline relying on
the synthesis of people, policy, education,
training, awareness, procedures, and
technology to improve protection of an
organization’s information assets
 Technical solutions can maintain
– Confidentiality, Integrity & Availability of
information
– In each of its three states
• Storage
• Transmission
• processing
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Physical Design of the SecSDLC
The physical design phase of the
SecSDLC is made up of two parts:
– security technologies
– physical security
Physical design takes the logical
design, expressed by the information
security blueprint and the contingency
planning elements and extends the
design to the next level
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Physical Design of the SecSDLC
Analyze
Physical Design:
Security Technologies
Chapter 8
Physical Design:
Physical Security
Chapter 9
Logical Design
Implement
Maintain
FIG URE 8-1 Physical Design within the SecSDLCPhysical Design within the SecSDLC
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Physical Design of the SecSDLC
 The physical design phase encompasses the
selection of technologies and processes to
manage risk
 At the end of the physical design phase you
have:
– Selected technologies needed to support the information
security blueprint
– Defined what the successful solution for a secured
environment will encompass
– Designed physical security measures that support the
technical solutions
– Prepared to create project plans in the implementation
phase to follow
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Firewalls
 A firewall is any device that prevents a
specific type of information from moving
between the untrusted network outside and
the trusted network inside
 There are five recognized generations of
firewalls
 The firewall may be:
– a separate computer system
– a service running on an existing router or server
– a separate network containing a number of
supporting devices
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First Generation
 Called packet filtering firewalls
 Examines every incoming packet header and
selectively filters packets based on
– address, packet type, port request, and others
factors
 The restrictions most commonly
implemented are based on:
– IP source and destination address
– Direction (inbound or outbound)
– TCP or UDP source and destination port-requests
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Packet Filtering Firewall
Packet filtering router
used as a first generation
firewall Trusted network
Untrusted
Network
FilteredFiltered
Data PacketsData Packets
UnrestrictedUnrestricted
Data PacketsData Packets
BlockedBlocked
Data PacketsData Packets
FIGURE 8-2 Packet Filtering Firewall
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Second Generation
 Called application-level firewall or proxy server
 Often a dedicated computer separate from the
filtering router
 With this configuration the proxy server, rather
than the Web server, is exposed to the outside world
in the DMZ
 Additional filtering routers can be implemented
behind the proxy server
 The primary disadvantage of application-level
firewalls is that they are designed for a specific
protocol and cannot easily be reconfigured to protect
against attacks on protocols for which they are not
designed
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Third Generation
 Called stateful inspection firewalls
 Keeps track of each network connection
established between internal and external
systems using a state table which tracks the
state and context of each packet in the
conversation by recording which station sent
what packet and when
 If the stateful firewall receives an incoming
packet that it cannot match in its state
table, then it defaults to its ACL to
determine whether to allow the packet to
pass
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Third Generation
 The primary disadvantage is the additional
processing requirements of managing and
verifying packets against the state table
which can possibly expose the system to a
DoS attack
 These firewalls can track connectionless
packet traffic such as UDP and remote
procedure calls (RPC) traffic
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Fourth Generation
 A dynamic packet filtering firewall allows only a
particular packet with a particular source,
destination, and port address to enter through the
firewall
 Does this by understanding how the protocol
functions, and opening and closing “doors” in the
firewall, based on the information contained in the
packet header
 In this manner, dynamic packet filters are an
intermediate form, between traditional static packet
filters and application proxies
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Fifth Generation
The final form of firewall is the kernel
proxy, a specialized form that works
under the Windows NT Executive,
which is the kernel of Windows NT
It evaluates packets at multiple layers
of the protocol stack, by checking
security in the kernel as data is
passed up and down the stack
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Packet-filtering Routers
Most organizations with an Internet
connection have some form of a router
as the interface at the perimeter
between the organization’s internal
networks and the external service
provider
Many of these routers can be
configured to filter packets that the
organization does not allow into the
network
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Packet-filtering Routers
This is a simple but effective means
to lower the organization’s risk to
external attack
The drawback to this type of system
includes a lack of auditing and strong
authentication
The complexity of the access control
lists used to filter the packets can
grow and degrade network
performance
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Screened-Host Firewall Systems
 Combine the packet-filtering router with a separate,
dedicated firewall such as an application proxy
server
 Allows the router to pre-screen packets to minimize
the network traffic and load on the internal proxy
 Application proxy examines an application layer
protocol, such as HTTP, and performs the proxy
services
 This separate host often referred to as a bastion-
host, as it represents a single, rich target for
external attacks, and should be very thoroughly
secured
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Filtered
Data
Packets
Screened-Host Firewall
Trusted network
Untrusted
Network
Unrestricted
Data Packets
Blocked
Data Packets
FIGURE 8-3 Screened Host Firewall
Bastion-host
Application Level
Firewall
Proxy access
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Dual-homed Host Firewalls
 The bastion-host contains two NICs (network
interface cards)
 One NIC connected to the external network,
and one connected to the internal network
 With two NICs all traffic must physically go
through the firewall to move between the
internal and external networks
 A technology known as network-address
translation (NAT) is commonly implemented
with this architecture to map from real,
valid, external IP addresses to ranges of
internal IP addresses that are non-routable
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Dual-homed Host Firewall
Trusted network
Untrusted
Network
Unrestricted
Data Packets
Blocked External
Data Packets
FIGURE 8-4 Dual-homed Host Firewall
Dual-homed Host
used as a firewall providing
Network Address Translation
(NAT)
External
filtering router
Internal
filtering router
Public IP Addresses NAT assigned local addresses
Blocked Internal
Data Packets
Proxy Access
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Screened-Subnet Firewalls (with DMZ)
Consists of two or more internal
bastion-hosts, behind a packet-filtering
router, with each host protecting the
trusted network
The first general model consists of two
filtering routers, with one or more
dual-homed bastion-host between
them
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Screened-Subnet Firewalls (with DMZ)
 The second general model involves the
connection from the outside or untrusted
network going through this path:
– Through an external filtering router
– Into and then out of a routing firewall to the
separate network segment known as the DMZ
 Connections into the trusted internal
network are allowed only from the DMZ
bastion-host servers
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Screened-Subnet Firewall
Trusted network
Untrusted
Network
Blocked
Data Packets
Proxy access
FIGURE 8-5 Screened Subnet (DMZ)
External
filtering router Internal
filtering router
Controlled access
Demilitarized zone
(DMZ)
ServersServers
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SOCKS Servers
 The SOCKS system is a proprietary circuit-level
proxy server that places special SOCKS client-side
agents on each workstation
 Places the filtering requirements on the individual
workstation, rather than on a single point of defense
(and thus point of failure)
 This frees the entry router of filtering
responsibilities, but then requires each workstation
to be managed as a firewall detection and protection
device
 A SOCKS system can require additional support and
management resources to configure and manage
possibly hundreds of individual clients, versus a
single device or set of devices
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Selecting the Right Firewall
 What type of firewall technology offers the
right balance of protection features and cost
for the needs of the organization?
 What features are included in the base price?
What features are available at extra cost?
Are all cost factors known?
 How easy is it to set up and configure the
firewall? How accessible are staff technicians
with the mastery to do it well?
 Can the candidate firewall adapt to the
growing network in the target organization?
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Configuring and Managing Firewalls
 Each firewall device will have its own set of
configuration rules that regulate its actions
 Simple mistakes can turn the device into a
choke point
 When security rules conflict with the
performance of business, security loses since
organizations are much more willing to live
with a potential risk than a certain failure
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Firewall Recommended Practices
 All traffic from the trusted network is allowed out
 The firewall device is always inaccessible directly
from the public network
 Allow Simple Mail Transport Protocol (SMTP) data
to pass through your firewall, but insure it is all
routed to a well-configured SMTP gateway to filter
and route messaging traffic securely
 All Internet Control Message Protocol (ICMP) data
should be denied
 Block telnet (terminal emulation) access to all
internal servers from the public networks
 When Web services are offered outside the firewall,
deny HTTP traffic from reaching your internal
networks by using some form of proxy access or
DMZ architecture
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Dial-Up Protection
 While internal network connection via
private networks are now less popular due to
the high cost of installation, maintenance,
and protection, dial-up connections are still
quite common
 Unsecured, dial-up access represents a
substantial exposure to attack
– An attacker who suspects that an organization
has dial-up lines can use a device called a war-
dialer to locate the connection points
 For the most part, simple username and
password schemes are the only means of
authentication
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Remote Authentication Dial-in User Service
 RADIUS system centralizes management of user
authentication by placing the responsibility for
authenticating each user in the central RADIUS
server
Radius serverRemote access server(RAS)
1. Remote worker dials RAS and submits username and password
2. RAS passes username and password to RADIUS server
3. RADIUS server approves or rejects request and provides access authorization
4. RAS provides access to authorized remote worker
(1) (2)
(3)(4)
Tele-worker
FIGURE 8-6 RADIUS Configuration
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Terminal Access Controller Access Control System
TACACS contains a centralized
database, such as RADIUS, and
validates the user’s credentials at the
TACACS server
There are three versions of TACACS
– TACACS
– Extended TACACS
– TACACS+
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Intrusion Detection Systems (IDSs)
 IDSs work like burglar alarms
 IDSs require complex configurations to
provide the level of detection and response
desired
 An IDS operates as either network-based,
when the technology is focused on protecting
network information assets, or host-based,
when the technology is focused on protecting
server or host information assets
 IDSs use one of two detection methods,
signature-based or statistical anomaly-based
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Intrusion Detection System
External
Router
Host IDS: Examines the data in files
stored on host and alerts systems
administrators to any any changes
Network IDS: Examines packets
on network and alerts admin to
unusual patterns.
Header
0100101011Untrusted
Network
FIGURE 8-7 Intrusion Detection Systems
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Host-based IDSs
 Resides on a particular computer or server
(known as the host) and monitors activity on
that system.
 Most work on principle of configuration or
change management, in which the systems
record the file sizes, locations, and other
attributes, and reports when one or more of
these attributes changes, when new files are
created, and when existing files are deleted.
 Can also monitor systems logs for pre-
defined events.
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Host-based IDSs
 Maintains own log files so when hackers
successfully modify a systems log the IDS
provides independent verification of the
attack Once properly configured, host-IDSs
are very reliable.
 Managed host-based IDS can monitor
multiple computers simultaneously.
– Stores a client file on each monitored host
– Has that host report back to the master console
(usually located on the sysadmin’s computer)
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Host-based IDS
Host-based
IDS
FIGURE 8-8
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Network-based IDSs
 Works differently than its host-based
counterpart; monitors network traffic
 When a pre-defined condition occurs, it
responds and notifies the appropriate
administrator
 Must match known and unknown attack
strategies against knowledge base to
determine if an attack has occurred
 Result in more false positive readings than
do host-based IDSs
– System is attempting to read into the pattern of
activity on the network to determine what is
normal and what is not
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Network-based IDS
Network-
based
IDS
FIGURE 8-8
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Signature-based IDSs
 AKA knowledge-based IDS; examines data
traffic looking for something that matches
signatures, which are pre-configured,
predetermined attack patterns
 Problem: signatures must be continually
updated as new attack strategies are
identified
 Attackers who are slow and methodical may
slip undetected through the IDS, as actions
may not match the signature that includes
factors based on duration of the events
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Statistical Anomaly-based IDSs
AKA behavior-based IDS
Collects data from normal traffic and
establishes a baseline
Once the baseline is established,
periodically samples network activity,
based on statistical methods, and
compares samples to baseline
If activity is outside baseline
parameters (known as a clipping level),
IDS notifies administrator
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Statistical Anomaly-based IDSs
 Advantage: system able to detect new types of
attacks as it looks for abnormal activity of any
type
 Unfortunately require much more overhead
and processing capacity than signature-based
versions, as they must constantly attempt to
pattern matched activity to the baseline
 Also may not detect minor changes to systems
variables can generate many false positives
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Scanning And Analysis Tools
 Used to collect information needed by an
attacker to succeed
 One of the preparatory parts of an attack is
collection of information about a potential
target, a process called footprinting
– Organized research of the Internet addresses
owned or controlled by a target organization
 Attacker uses public Internet data sources to
perform keyword searches to identify the
network addresses of the organization
 This research augmented with browsing
organization’s Web pages
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Scanning And Analysis Tools
Next phase of the pre-attack data
gathering process: fingerprinting
Systematic examination of all Internet
addresses of the organization (collected
during the footprinting)
Accomplished with tools discussed in
the next section, fingerprinting reveals
useful information for the anticipated
attack
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Scanning And Analysis Tools
Scanners, sniffers, and other analysis
tools are invaluable to security
administrators; enables them to see
what the attacker sees
Can find vulnerabilities in systems,
holes in security components, and
unsecured aspects of the network
– Unfortunately, they cannot detect the
unpredictable behavior of people.
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Scanning And Analysis Tools
Many of these tools have distinct
signatures & some Internet service
providers (ISPs) scan for these
signatures.
– If an ISP discovers someone using
“hacker tools” it can pull access privileges
– Best to establish working relationship
with the ISP & notify them of the purpose
and extent of the signatures.
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Port Scanners
 Port scanners fingerprint networks to find
ports and services and other useful
information
 Why secure open ports?
– An open port can be used to send commands to a
computer, gain access to a server, and exert
control over a networking device
– The general rule of thumb is to remove from
service or secure any port not absolutely
necessary for the conduct of business
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Well-known Port Numbers
Port numbers Description
20 and 21 File Transfer Protocol (FTP)
25 Simple Mail Transfer Protocol (SMTP)
53 Domain Name Services (DNS)
67 and 68 Dynamic Host Configuration Protocol (DHCP)
80 Hypertext Transfer Protocol (HTTP)
110 Post Office Protocol (POP3)
161 Simple Network Management Protocol (SNMP)
194 IRC Chat port (used for device sharing)
443 HTTP over SSL
8080 Used for proxy services
Table 8-2 Well-known Port Numbers
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Source:http://support.gfi.com/manuals/en/lanscan2/analyzingthescanresults.htm
FIGURE 8-11
LANGuard
Network Scanner
LANguard Network Scanner
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Vulnerability Scanners
Vulnerability scanners are capable of
scanning networks for very detailed
information
As a class, they identify exposed
usernames and groups, show open
network shares, expose configuration
problems, and other vulnerabilities
in servers
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Source:http://www.insecure.org/nmap/images/nmapfe.gif
Nmap Vulnerability Scanner
FIGURE 8-12
Nmap Vulnerability Scanner
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Packet Sniffers
 A network tool that collects copies of
packets from the network and analyzes
them
 Can be used to eavesdrop on the network
traffic
 To use a packet sniffer legally, you must be:
– on a network that the organization owns
– under direct authorization of the owners of the
network
– have knowledge and consent of the content
creators (users)
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Source http://www.ethereal.com/docs/user-guide/x885.html
Ethereal Sample Screen
FIGURE 8-13
Ethereal
Sample Screen
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Content Filters
Although technically not a firewall, a
content filter is a software filter that
allows administrators to restrict
accessible content from within a
network
The content filtering restricts Web
sites with inappropriate content
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Trap and Trace
 Software designed to entice individuals
illegally perusing the internal areas of a
network
 Better known as honey pots, they distract
the attacker while notifying the
administrator
 Trace: attempt to determine the identity of
someone using unauthorized access
– Main purpose: capture system abusers internal to
the network
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Cryptography and Encryption
Sophisticated approach to security
Many security-related tools use
embedded encryption technologies
Encryption is the process of converting
an original message into a form that is
unreadable by unauthorized
individuals
The science of encryption, known as
cryptology, encompasses cryptography
and cryptanalysis
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Encryption Definitions
 Algorithm: the mathematical formula used to
convert an unencrypted message into an encrypted
message.
 Cipher: the transformation of the individual
components (characters, bytes, or bits) of an
unencrypted message into encrypted components.
 Ciphertext or cryptogram: the unintelligible
encrypted or encoded message resulting from an
encryption.
 Code: the transformation of the larger components
(words or phrases) of an unencrypted message into
encrypted components.
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Encryption Definitions
 Cryptosystem: the set of transformations necessary
to convert an unencrypted message into an
encrypted message.
 Decipher: to decrypt or convert ciphertext to
plaintext.
 Encipher: to encrypt or convert plaintext to
ciphertext.
 Key or cryptovariable: the information used in
conjunction with the algorithm to create ciphertext
from plaintext.
 Keyspace: the entire range of values that can
possibly be used to construct an individual key.
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Encryption Definitions
 Link encryption: a series of encryptions and
decryptions between a number of systems, whereby
each node decrypts the message sent to it and then
re-encrypts it using different keys and sends it to
the next neighbor, until it reaches the final
destination.
 Plaintext: the original unencrypted message that is
encrypted and results from successful decryption.
 Steganography: the process of hiding messages in a
picture or graphic.
 Work factor: the amount of effort (usually in hours)
required to perform cryptanalysis on an encoded
message.
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Cryptography & Encryption-Based Solutions
 Simple forms of encryption are based on two
concepts: the block cipher and the exclusive
OR operation
 With the block cipher method
– the message is divided into blocks, i.e., 8 or 16 bit
– and then each block is transformed using the
algorithm and key
 The “exclusive or operation” (XOR) is a
function of Boolean algebra
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Exclusive OR Operations
Bit 1 Bit 2 Exclusive OR result
0 0 0
0 1 1
1 0 1
1 1 0
Exclusive OR OperationsTABLE 8-3
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Encryption Algorithms
 In encryption the most commonly used
algorithms include two functions:
substitution and transposition
 In a substitution cipher, you substitute one
value for another
 This type of substitution is based on a
monoalphabetic substitution, since it only
uses one alphabet
 More advanced substitution ciphers use two
or more alphabets, and are referred to as
polyalphabetic substitutions
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Encryption Operations
 Just like the substitution operation, the
transposition cipher is simple to understand
but can be complex to decipher if properly
used
 Unlike the substitution cipher, the
transposition cipher (or permutation cipher)
simply rearranges the values within a block
to create the ciphertext
 This can be done at the bit level or at the
byte (character) level - transposition ciphers
move these bits or bytes to another location
in the block, so that bit 1 becomes bit 4, bit 2
becomes bit 7 etc
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Vernam Cipher
 Also known as the one-time pad, the Vernam
cipher was developed at AT&T and uses a
one-use set of characters, the value of which
is added to the block of text
 The resulting sum is then converted to text
 When the two are added, if the values
exceed 26, 26 is subtracted from the total
(Modulo 26) - the corresponding results are
then converted back to text
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Book or Running Key Cipher
 Another method, made popular by spy
movies, is the use of text in a book as the
algorithm to decrypt a message
 The key consists of
– knowing which book to use
– a list of codes representing the page number, line
number, and word number of the plaintext word
 Dictionaries and thesauruses make the most
popular sources as they guarantee every
word needed, although almost any book will
suffice
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Symmetric Encryption
 The same key, also known as a secret key
used to conduct both encryption and
decryption of the message
 Can be extremely efficient, requiring minimal
processing to either encrypt or decrypt the
message
 Problem: both sender & receiver must own
the encryption key
– If either copy of the key is compromised, an
intermediate can decrypt and read the messages
 Challenges: get copy of the key to the
receiver, a process that must be conducted
out-of-band to avoid interception
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Symmetric Encryption
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Data Encryption Standard (DES)
Developed in 1977 by IBM
Based on the Data Encryption
Algorithm (DEA)
Uses a 64-bit block size and a 56-bit
key
With a 56-bit key, the algorithm has
256 possible keys to choose from (over
72 quadrillion)
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Data Encryption Standard (DES)
 DES is a federally approved standard for
non classified data
 RSA put a bounty on the algorithm offering
$10,000 to the team to crack the algorithm
 Fourteen thousand users collaborated over
the Internet to finally break the encryption
 On 19 October 1997 at 1325 UTC, the 56 bit
DES algorithm was cracked by a distributed
processing system coordinated by a
computer in my lab at IIT’s Main Campus
ITM 578 69
ILLINOIS INSTITUTE OF TECHNOLOGY
Triple DES (3DES)
 Developed as an improvement to DES
 Uses up to three keys in succession and also
performs three different encryption
operations:
– 3DES encrypts the message three times with
three different keys, the most secure level of
encryption possible with 3DES
 In 1998, it took a dedicated computer
designed by the Electronic Freedom Frontier
(www.eff.org) over 56 hours to crack DES
ITM 578 70
ILLINOIS INSTITUTE OF TECHNOLOGY
Advanced Encryption Standard
(AES)
The successor to 3DES is Advanced
Encryption Standard (AES), based on
the Rijndael Block Cipher, a block
cipher with a variable block length
and a key length of either128, 192, or
256 bits
It would take the same computer
approximately 4,698,864 quintillion
years to crack AES
ITM 578 71
ILLINOIS INSTITUTE OF TECHNOLOGY
Asymmetric Encryption
 Best known as public key encryption
 Uses two different keys
 Either key can be used to encrypt or decrypt
the message, however, if Key A is used to
encrypt the message, only Key B can decrypt,
and if Key B is used to encrypt a message,
only Key A can decrypt it.
 Public key is stored in a public location,
where anyone can use it
 Private key is a secret known only to the
owner of the key pair
ITM 578 72
ILLINOIS INSTITUTE OF TECHNOLOGY
Using Public Keys
ITM 578 73
ILLINOIS INSTITUTE OF TECHNOLOGY
Digital Signatures
 An interesting thing happens when the
asymmetric process is reversed, that is the
private key is used to encrypt a short
message
 The public key can be used to decrypt it, and
the fact that the message was sent by the
organization that owns the private key
cannot be refuted
 This is known as nonrepudiation, which is
the foundation of digital signatures
 Digital Signatures are encrypted messages
that are independently verified by a central
facility (registry) as authentic
ITM 578 74
ILLINOIS INSTITUTE OF TECHNOLOGY
RSA
 One of the most popular public key
cryptosystems
 Stands for Rivest-Shamir-Aldeman, its
developers
 First public key encryption algorithm
developed and published for commercial use
 Part of Web browsers from both Microsoft
and Netscape
 56 bit version is not secure; 128 bit version is
acceptable
ITM 578 75
ILLINOIS INSTITUTE OF TECHNOLOGY
PKI or Public Key Infrastructure
 Public Key Infrastructure is the entire set of
hardware, software, and cryptosystems
necessary to implement public key
encryption
 PKI systems are based on public-key
cryptosystems and include digital
certificates and certificate authorities (CAs)
and can:
– Issue digital certificates
– Issue crypto keys
– Provide tools to use crypto to secure information
– Provide verification and return of certificates
ITM 578 76
ILLINOIS INSTITUTE OF TECHNOLOGY
PKI Benefits
PKI protects information assets in
several ways:
– Authentication
– Integrity
– Privacy
– Authorization
– Nonrepudiation
ITM 578 77
ILLINOIS INSTITUTE OF TECHNOLOGY
Digital Certificates & Certificate Authorities
 A digital certificate is an electronic
document, similar to a digital signature,
attached to a file certifying that this file is
from the organization it claims to be from
and has not been modified from the original
format
 A Certificate Authority is an agency that
manages the issuance of certificates and
serves as the electronic notary public to
verify their worth and integrity
ITM 578 78
ILLINOIS INSTITUTE OF TECHNOLOGY
Hybrid Systems
 In practice, pure asymmetric key encryption not
widely used except in the area of certificates
 More often used in conjunction with symmetric
key encryption creating a hybrid system
 Use the Diffie-Hellman Key Exchange method
that uses asymmetric techniques to exchange
symmetric keys to enable efficient, secure
communications based on symmetric keys
 Diffie-Hellman provided the foundation for
subsequent developments in public key
encryption
ITM 578 79
ILLINOIS INSTITUTE OF TECHNOLOGY
Hybrid Encryption Example
ITM 578 80
ILLINOIS INSTITUTE OF TECHNOLOGY
Securing E-mail
 Encryption cryptosystems have been
adapted to inject some degree of security
into e-mail:
– S/MIME builds on the Multipurpose Internet
Mail Extensions (MIME) encoding format by
adding encryption and authentication
– Privacy Enhanced Mail (PEM) was proposed by
the Internet Engineering Task Force (IETF) as a
standard to function with the public key
cryptosystems
– PEM uses 3DES symmetric key encryption and
RSA for key exchanges and digital signatures
– Pretty Good Privacy (PGP), developed by Phil
Zimmerman, uses the IDEA Cipher along with
RSA for key exchange
ITM 578 81
ILLINOIS INSTITUTE OF TECHNOLOGY
Securing the Web
Secure Electronic Transactions (SET)
Secure Socket Layer (SSL)
Secure Hypertext Transfer Protocol
(SHTTP)
Secure Shell (SSH)
IPSec
ITM 578 82
ILLINOIS INSTITUTE OF TECHNOLOGY
IPSec
 IP Security (IPSec) is the cryptographic
authentication and encryption product of the
IETF’s IP Protocol Security Working Group
 Defined in RFC 1825, 1826, and 1827
 Used to create Virtual Private Networks
(VPNs) and is an open framework for
security development within the TCP/IP
family of protocol standards
 Combines several different cryptosystem
elements and includes:
– the IP Security Protocol itself
– the Internet Key Exchange
ITM 578 83
ILLINOIS INSTITUTE OF TECHNOLOGY
IPSec Operations
 IPSec works in two modes of operation:
– In transport mode only the IP data is encrypted,
not the IP headers themselves
– In tunnel mode, the entire IP packet is encrypted
and is then placed as the payload in another IP
packet
 The implementation of these technologies is
very popular through a process known as
Virtual Private Networks (VPNs)
 In the most common implementation, a VPN
allows a user to turn the Internet into a
private network between points on the
public network
ITM 578 84
ILLINOIS INSTITUTE OF TECHNOLOGY
Kerberos Scenario: Initial Login
ITM 578 85
ILLINOIS INSTITUTE OF TECHNOLOGY
Kerberos Scenario: Request for Services
ITM 578 86
ILLINOIS INSTITUTE OF TECHNOLOGY
Sesame
 To solve some of the problems associated
with Kerberos, a new project, the Secure
European System for Applications in a
Multivendor Environment (SESAME), was
developed as a European research and
development project, partly funded by the
European Commission
 SESAME is similar in part to Kerberos in
that the user is first authenticated to an
authentication server to receive a token
ITM 578 87
ILLINOIS INSTITUTE OF TECHNOLOGY
Access Control Devices
 To insure secure operation, access control needs
strong authentication (two-factor authentication)
 Consist of the user’s personal password or
passphrase but requires at least one other factor to
represent strong authentication
 Frequently a physical device is used for the second
factor
 When considering access control you address:
– What you know
– What you have
– Who you are
– What you produce
ITM 578 88
ILLINOIS INSTITUTE OF TECHNOLOGY
What You Are - Biometrics
 Most of the technologies that scan human
characteristics convert these images to some
form of minutiae
 Minutiae are unique points of reference that
are digitized and stored in an encrypted
format
 Each subsequent scan is also digitized and
then compared with the encoded value to
determine if users are who they claim to be
 The problem is that some human
characteristics can change over time, due to
normal development, injury, or illness
ITM 578 89
ILLINOIS INSTITUTE OF TECHNOLOGY
Voice recognition
Signature recognition
Hand
geometry
Hand and palm
print
Fingerprint Iris
recognition
Retinal
Recognition
Facial
geometry
Recognition Characteristics
FIGURE 8-20
Recognition Characteristics
ITM 578 90
ILLINOIS INSTITUTE OF TECHNOLOGY
Effectiveness of Biometrics
Biometric technologies are evaluated
on three basic criteria:
–False Reject Rate
–False Accept Rate
–Crossover Error Rate
ITM 578 91
ILLINOIS INSTITUTE OF TECHNOLOGY
False Reject Rate (FRR)
The percentage or value associated
with the rate at which authentic users
are denied or prevented access to
authorized areas, as a result of a
failure in the biometric device
Type I error
Probably of the least concern to
security
ITM 578 92
ILLINOIS INSTITUTE OF TECHNOLOGY
False Accept Rate (FAR)
The percentage or value associated
with the rate at which fraudulent or
non-users are allowed access to
systems or areas, as a result of a
failure in the biometric device
Type II error
This type of error is unacceptable to
security, as it represents a clear
breach
ITM 578 93
ILLINOIS INSTITUTE OF TECHNOLOGY
Crossover Error Rate (CER)
The crossover error rate is the point
at which the number of false
rejections equals the false
acceptances, also known as the equal
error rate
It is possibly the most common and
important overall measure of the
accuracy of a biometric system
The optimal setting is somewhere
near the equal error rate or CER
ITM 578 94
ILLINOIS INSTITUTE OF TECHNOLOGY
Acceptability of Biometrics
While the use of one authentication
area is necessary to access the
system, the more devices used the
better
To obtain strong authentication, the
systems must use two or more
authentication areas
ITM 578 95
ILLINOIS INSTITUTE OF TECHNOLOGY
The End…
Questions?

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Security technologies

  • 1. TransformingLives. InventingtheFuture. www.iit.edu I ELLINOIS T UINS TI T OF TECHNOLOGY ITM 578 1 Security Technologies Ray Trygstad ITM 478/578 Spring 2004 Master of Information Technology & Management Program CenterforProfessional Development Slides based on Whitman, M. and Mattord, H., Principles of InformationSecurity; Thomson Course Technology 2003
  • 2. ITM 578 2 ILLINOIS INSTITUTE OF TECHNOLOGY Learning Objectives: Upon completion of this lesson the student should be able to: – Define and identify the various types of firewalls. – Discuss the approaches to firewall implementation. – Discuss the approaches to dial-up access and protection. – Identify and describe the two categories of intrusion detection systems. – Discuss the two strategies behind intrusion detection systems.
  • 3. ITM 578 3 ILLINOIS INSTITUTE OF TECHNOLOGY Learning Objectives: Upon completion of this lesson the student should be able to: – Discuss scanning, analysis tools, and content filters. – Understand trap and trace technologies. – Discuss the process of encryption and define key terms. – Identify and discuss common approaches to cryptography. – Compare and contrast symmetric and asymmetric encryption. – Discuss various approaches to biometric access control.
  • 4. ITM 578 4 ILLINOIS INSTITUTE OF TECHNOLOGY Introduction  Information security: a discipline relying on the synthesis of people, policy, education, training, awareness, procedures, and technology to improve protection of an organization’s information assets  Technical solutions can maintain – Confidentiality, Integrity & Availability of information – In each of its three states • Storage • Transmission • processing
  • 5. ITM 578 5 ILLINOIS INSTITUTE OF TECHNOLOGY Physical Design of the SecSDLC The physical design phase of the SecSDLC is made up of two parts: – security technologies – physical security Physical design takes the logical design, expressed by the information security blueprint and the contingency planning elements and extends the design to the next level
  • 6. ITM 578 6 ILLINOIS INSTITUTE OF TECHNOLOGY Physical Design of the SecSDLC Analyze Physical Design: Security Technologies Chapter 8 Physical Design: Physical Security Chapter 9 Logical Design Implement Maintain FIG URE 8-1 Physical Design within the SecSDLCPhysical Design within the SecSDLC
  • 7. ITM 578 7 ILLINOIS INSTITUTE OF TECHNOLOGY Physical Design of the SecSDLC  The physical design phase encompasses the selection of technologies and processes to manage risk  At the end of the physical design phase you have: – Selected technologies needed to support the information security blueprint – Defined what the successful solution for a secured environment will encompass – Designed physical security measures that support the technical solutions – Prepared to create project plans in the implementation phase to follow
  • 8. ITM 578 8 ILLINOIS INSTITUTE OF TECHNOLOGY Firewalls  A firewall is any device that prevents a specific type of information from moving between the untrusted network outside and the trusted network inside  There are five recognized generations of firewalls  The firewall may be: – a separate computer system – a service running on an existing router or server – a separate network containing a number of supporting devices
  • 9. ITM 578 9 ILLINOIS INSTITUTE OF TECHNOLOGY First Generation  Called packet filtering firewalls  Examines every incoming packet header and selectively filters packets based on – address, packet type, port request, and others factors  The restrictions most commonly implemented are based on: – IP source and destination address – Direction (inbound or outbound) – TCP or UDP source and destination port-requests
  • 10. ITM 578 10 ILLINOIS INSTITUTE OF TECHNOLOGY Packet Filtering Firewall Packet filtering router used as a first generation firewall Trusted network Untrusted Network FilteredFiltered Data PacketsData Packets UnrestrictedUnrestricted Data PacketsData Packets BlockedBlocked Data PacketsData Packets FIGURE 8-2 Packet Filtering Firewall
  • 11. ITM 578 11 ILLINOIS INSTITUTE OF TECHNOLOGY Second Generation  Called application-level firewall or proxy server  Often a dedicated computer separate from the filtering router  With this configuration the proxy server, rather than the Web server, is exposed to the outside world in the DMZ  Additional filtering routers can be implemented behind the proxy server  The primary disadvantage of application-level firewalls is that they are designed for a specific protocol and cannot easily be reconfigured to protect against attacks on protocols for which they are not designed
  • 12. ITM 578 12 ILLINOIS INSTITUTE OF TECHNOLOGY Third Generation  Called stateful inspection firewalls  Keeps track of each network connection established between internal and external systems using a state table which tracks the state and context of each packet in the conversation by recording which station sent what packet and when  If the stateful firewall receives an incoming packet that it cannot match in its state table, then it defaults to its ACL to determine whether to allow the packet to pass
  • 13. ITM 578 13 ILLINOIS INSTITUTE OF TECHNOLOGY Third Generation  The primary disadvantage is the additional processing requirements of managing and verifying packets against the state table which can possibly expose the system to a DoS attack  These firewalls can track connectionless packet traffic such as UDP and remote procedure calls (RPC) traffic
  • 14. ITM 578 14 ILLINOIS INSTITUTE OF TECHNOLOGY Fourth Generation  A dynamic packet filtering firewall allows only a particular packet with a particular source, destination, and port address to enter through the firewall  Does this by understanding how the protocol functions, and opening and closing “doors” in the firewall, based on the information contained in the packet header  In this manner, dynamic packet filters are an intermediate form, between traditional static packet filters and application proxies
  • 15. ITM 578 15 ILLINOIS INSTITUTE OF TECHNOLOGY Fifth Generation The final form of firewall is the kernel proxy, a specialized form that works under the Windows NT Executive, which is the kernel of Windows NT It evaluates packets at multiple layers of the protocol stack, by checking security in the kernel as data is passed up and down the stack
  • 16. ITM 578 16 ILLINOIS INSTITUTE OF TECHNOLOGY Packet-filtering Routers Most organizations with an Internet connection have some form of a router as the interface at the perimeter between the organization’s internal networks and the external service provider Many of these routers can be configured to filter packets that the organization does not allow into the network
  • 17. ITM 578 17 ILLINOIS INSTITUTE OF TECHNOLOGY Packet-filtering Routers This is a simple but effective means to lower the organization’s risk to external attack The drawback to this type of system includes a lack of auditing and strong authentication The complexity of the access control lists used to filter the packets can grow and degrade network performance
  • 18. ITM 578 18 ILLINOIS INSTITUTE OF TECHNOLOGY Screened-Host Firewall Systems  Combine the packet-filtering router with a separate, dedicated firewall such as an application proxy server  Allows the router to pre-screen packets to minimize the network traffic and load on the internal proxy  Application proxy examines an application layer protocol, such as HTTP, and performs the proxy services  This separate host often referred to as a bastion- host, as it represents a single, rich target for external attacks, and should be very thoroughly secured
  • 19. ITM 578 19 ILLINOIS INSTITUTE OF TECHNOLOGY Filtered Data Packets Screened-Host Firewall Trusted network Untrusted Network Unrestricted Data Packets Blocked Data Packets FIGURE 8-3 Screened Host Firewall Bastion-host Application Level Firewall Proxy access
  • 20. ITM 578 20 ILLINOIS INSTITUTE OF TECHNOLOGY Dual-homed Host Firewalls  The bastion-host contains two NICs (network interface cards)  One NIC connected to the external network, and one connected to the internal network  With two NICs all traffic must physically go through the firewall to move between the internal and external networks  A technology known as network-address translation (NAT) is commonly implemented with this architecture to map from real, valid, external IP addresses to ranges of internal IP addresses that are non-routable
  • 21. ITM 578 21 ILLINOIS INSTITUTE OF TECHNOLOGY Dual-homed Host Firewall Trusted network Untrusted Network Unrestricted Data Packets Blocked External Data Packets FIGURE 8-4 Dual-homed Host Firewall Dual-homed Host used as a firewall providing Network Address Translation (NAT) External filtering router Internal filtering router Public IP Addresses NAT assigned local addresses Blocked Internal Data Packets Proxy Access
  • 22. ITM 578 22 ILLINOIS INSTITUTE OF TECHNOLOGY Screened-Subnet Firewalls (with DMZ) Consists of two or more internal bastion-hosts, behind a packet-filtering router, with each host protecting the trusted network The first general model consists of two filtering routers, with one or more dual-homed bastion-host between them
  • 23. ITM 578 23 ILLINOIS INSTITUTE OF TECHNOLOGY Screened-Subnet Firewalls (with DMZ)  The second general model involves the connection from the outside or untrusted network going through this path: – Through an external filtering router – Into and then out of a routing firewall to the separate network segment known as the DMZ  Connections into the trusted internal network are allowed only from the DMZ bastion-host servers
  • 24. ITM 578 24 ILLINOIS INSTITUTE OF TECHNOLOGY Screened-Subnet Firewall Trusted network Untrusted Network Blocked Data Packets Proxy access FIGURE 8-5 Screened Subnet (DMZ) External filtering router Internal filtering router Controlled access Demilitarized zone (DMZ) ServersServers
  • 25. ITM 578 25 ILLINOIS INSTITUTE OF TECHNOLOGY SOCKS Servers  The SOCKS system is a proprietary circuit-level proxy server that places special SOCKS client-side agents on each workstation  Places the filtering requirements on the individual workstation, rather than on a single point of defense (and thus point of failure)  This frees the entry router of filtering responsibilities, but then requires each workstation to be managed as a firewall detection and protection device  A SOCKS system can require additional support and management resources to configure and manage possibly hundreds of individual clients, versus a single device or set of devices
  • 26. ITM 578 26 ILLINOIS INSTITUTE OF TECHNOLOGY Selecting the Right Firewall  What type of firewall technology offers the right balance of protection features and cost for the needs of the organization?  What features are included in the base price? What features are available at extra cost? Are all cost factors known?  How easy is it to set up and configure the firewall? How accessible are staff technicians with the mastery to do it well?  Can the candidate firewall adapt to the growing network in the target organization?
  • 27. ITM 578 27 ILLINOIS INSTITUTE OF TECHNOLOGY Configuring and Managing Firewalls  Each firewall device will have its own set of configuration rules that regulate its actions  Simple mistakes can turn the device into a choke point  When security rules conflict with the performance of business, security loses since organizations are much more willing to live with a potential risk than a certain failure
  • 28. ITM 578 28 ILLINOIS INSTITUTE OF TECHNOLOGY Firewall Recommended Practices  All traffic from the trusted network is allowed out  The firewall device is always inaccessible directly from the public network  Allow Simple Mail Transport Protocol (SMTP) data to pass through your firewall, but insure it is all routed to a well-configured SMTP gateway to filter and route messaging traffic securely  All Internet Control Message Protocol (ICMP) data should be denied  Block telnet (terminal emulation) access to all internal servers from the public networks  When Web services are offered outside the firewall, deny HTTP traffic from reaching your internal networks by using some form of proxy access or DMZ architecture
  • 29. ITM 578 29 ILLINOIS INSTITUTE OF TECHNOLOGY Dial-Up Protection  While internal network connection via private networks are now less popular due to the high cost of installation, maintenance, and protection, dial-up connections are still quite common  Unsecured, dial-up access represents a substantial exposure to attack – An attacker who suspects that an organization has dial-up lines can use a device called a war- dialer to locate the connection points  For the most part, simple username and password schemes are the only means of authentication
  • 30. ITM 578 30 ILLINOIS INSTITUTE OF TECHNOLOGY Remote Authentication Dial-in User Service  RADIUS system centralizes management of user authentication by placing the responsibility for authenticating each user in the central RADIUS server Radius serverRemote access server(RAS) 1. Remote worker dials RAS and submits username and password 2. RAS passes username and password to RADIUS server 3. RADIUS server approves or rejects request and provides access authorization 4. RAS provides access to authorized remote worker (1) (2) (3)(4) Tele-worker FIGURE 8-6 RADIUS Configuration
  • 31. ITM 578 31 ILLINOIS INSTITUTE OF TECHNOLOGY Terminal Access Controller Access Control System TACACS contains a centralized database, such as RADIUS, and validates the user’s credentials at the TACACS server There are three versions of TACACS – TACACS – Extended TACACS – TACACS+
  • 32. ITM 578 32 ILLINOIS INSTITUTE OF TECHNOLOGY Intrusion Detection Systems (IDSs)  IDSs work like burglar alarms  IDSs require complex configurations to provide the level of detection and response desired  An IDS operates as either network-based, when the technology is focused on protecting network information assets, or host-based, when the technology is focused on protecting server or host information assets  IDSs use one of two detection methods, signature-based or statistical anomaly-based
  • 33. ITM 578 33 ILLINOIS INSTITUTE OF TECHNOLOGY Intrusion Detection System External Router Host IDS: Examines the data in files stored on host and alerts systems administrators to any any changes Network IDS: Examines packets on network and alerts admin to unusual patterns. Header 0100101011Untrusted Network FIGURE 8-7 Intrusion Detection Systems
  • 34. ITM 578 34 ILLINOIS INSTITUTE OF TECHNOLOGY Host-based IDSs  Resides on a particular computer or server (known as the host) and monitors activity on that system.  Most work on principle of configuration or change management, in which the systems record the file sizes, locations, and other attributes, and reports when one or more of these attributes changes, when new files are created, and when existing files are deleted.  Can also monitor systems logs for pre- defined events.
  • 35. ITM 578 35 ILLINOIS INSTITUTE OF TECHNOLOGY Host-based IDSs  Maintains own log files so when hackers successfully modify a systems log the IDS provides independent verification of the attack Once properly configured, host-IDSs are very reliable.  Managed host-based IDS can monitor multiple computers simultaneously. – Stores a client file on each monitored host – Has that host report back to the master console (usually located on the sysadmin’s computer)
  • 36. ITM 578 36 ILLINOIS INSTITUTE OF TECHNOLOGY Host-based IDS Host-based IDS FIGURE 8-8
  • 37. ITM 578 37 ILLINOIS INSTITUTE OF TECHNOLOGY Network-based IDSs  Works differently than its host-based counterpart; monitors network traffic  When a pre-defined condition occurs, it responds and notifies the appropriate administrator  Must match known and unknown attack strategies against knowledge base to determine if an attack has occurred  Result in more false positive readings than do host-based IDSs – System is attempting to read into the pattern of activity on the network to determine what is normal and what is not
  • 38. ITM 578 38 ILLINOIS INSTITUTE OF TECHNOLOGY Network-based IDS Network- based IDS FIGURE 8-8
  • 39. ITM 578 39 ILLINOIS INSTITUTE OF TECHNOLOGY Signature-based IDSs  AKA knowledge-based IDS; examines data traffic looking for something that matches signatures, which are pre-configured, predetermined attack patterns  Problem: signatures must be continually updated as new attack strategies are identified  Attackers who are slow and methodical may slip undetected through the IDS, as actions may not match the signature that includes factors based on duration of the events
  • 40. ITM 578 40 ILLINOIS INSTITUTE OF TECHNOLOGY Statistical Anomaly-based IDSs AKA behavior-based IDS Collects data from normal traffic and establishes a baseline Once the baseline is established, periodically samples network activity, based on statistical methods, and compares samples to baseline If activity is outside baseline parameters (known as a clipping level), IDS notifies administrator
  • 41. ITM 578 41 ILLINOIS INSTITUTE OF TECHNOLOGY Statistical Anomaly-based IDSs  Advantage: system able to detect new types of attacks as it looks for abnormal activity of any type  Unfortunately require much more overhead and processing capacity than signature-based versions, as they must constantly attempt to pattern matched activity to the baseline  Also may not detect minor changes to systems variables can generate many false positives
  • 42. ITM 578 42 ILLINOIS INSTITUTE OF TECHNOLOGY Scanning And Analysis Tools  Used to collect information needed by an attacker to succeed  One of the preparatory parts of an attack is collection of information about a potential target, a process called footprinting – Organized research of the Internet addresses owned or controlled by a target organization  Attacker uses public Internet data sources to perform keyword searches to identify the network addresses of the organization  This research augmented with browsing organization’s Web pages
  • 43. ITM 578 43 ILLINOIS INSTITUTE OF TECHNOLOGY Scanning And Analysis Tools Next phase of the pre-attack data gathering process: fingerprinting Systematic examination of all Internet addresses of the organization (collected during the footprinting) Accomplished with tools discussed in the next section, fingerprinting reveals useful information for the anticipated attack
  • 44. ITM 578 44 ILLINOIS INSTITUTE OF TECHNOLOGY Scanning And Analysis Tools Scanners, sniffers, and other analysis tools are invaluable to security administrators; enables them to see what the attacker sees Can find vulnerabilities in systems, holes in security components, and unsecured aspects of the network – Unfortunately, they cannot detect the unpredictable behavior of people.
  • 45. ITM 578 45 ILLINOIS INSTITUTE OF TECHNOLOGY Scanning And Analysis Tools Many of these tools have distinct signatures & some Internet service providers (ISPs) scan for these signatures. – If an ISP discovers someone using “hacker tools” it can pull access privileges – Best to establish working relationship with the ISP & notify them of the purpose and extent of the signatures.
  • 46. ITM 578 46 ILLINOIS INSTITUTE OF TECHNOLOGY Port Scanners  Port scanners fingerprint networks to find ports and services and other useful information  Why secure open ports? – An open port can be used to send commands to a computer, gain access to a server, and exert control over a networking device – The general rule of thumb is to remove from service or secure any port not absolutely necessary for the conduct of business
  • 47. ITM 578 47 ILLINOIS INSTITUTE OF TECHNOLOGY Well-known Port Numbers Port numbers Description 20 and 21 File Transfer Protocol (FTP) 25 Simple Mail Transfer Protocol (SMTP) 53 Domain Name Services (DNS) 67 and 68 Dynamic Host Configuration Protocol (DHCP) 80 Hypertext Transfer Protocol (HTTP) 110 Post Office Protocol (POP3) 161 Simple Network Management Protocol (SNMP) 194 IRC Chat port (used for device sharing) 443 HTTP over SSL 8080 Used for proxy services Table 8-2 Well-known Port Numbers
  • 48. ITM 578 48 ILLINOIS INSTITUTE OF TECHNOLOGY Source:http://support.gfi.com/manuals/en/lanscan2/analyzingthescanresults.htm FIGURE 8-11 LANGuard Network Scanner LANguard Network Scanner
  • 49. ITM 578 49 ILLINOIS INSTITUTE OF TECHNOLOGY Vulnerability Scanners Vulnerability scanners are capable of scanning networks for very detailed information As a class, they identify exposed usernames and groups, show open network shares, expose configuration problems, and other vulnerabilities in servers
  • 50. ITM 578 50 ILLINOIS INSTITUTE OF TECHNOLOGY Source:http://www.insecure.org/nmap/images/nmapfe.gif Nmap Vulnerability Scanner FIGURE 8-12 Nmap Vulnerability Scanner
  • 51. ITM 578 51 ILLINOIS INSTITUTE OF TECHNOLOGY Packet Sniffers  A network tool that collects copies of packets from the network and analyzes them  Can be used to eavesdrop on the network traffic  To use a packet sniffer legally, you must be: – on a network that the organization owns – under direct authorization of the owners of the network – have knowledge and consent of the content creators (users)
  • 52. ITM 578 52 ILLINOIS INSTITUTE OF TECHNOLOGY Source http://www.ethereal.com/docs/user-guide/x885.html Ethereal Sample Screen FIGURE 8-13 Ethereal Sample Screen
  • 53. ITM 578 53 ILLINOIS INSTITUTE OF TECHNOLOGY Content Filters Although technically not a firewall, a content filter is a software filter that allows administrators to restrict accessible content from within a network The content filtering restricts Web sites with inappropriate content
  • 54. ITM 578 54 ILLINOIS INSTITUTE OF TECHNOLOGY Trap and Trace  Software designed to entice individuals illegally perusing the internal areas of a network  Better known as honey pots, they distract the attacker while notifying the administrator  Trace: attempt to determine the identity of someone using unauthorized access – Main purpose: capture system abusers internal to the network
  • 55. ITM 578 55 ILLINOIS INSTITUTE OF TECHNOLOGY Cryptography and Encryption Sophisticated approach to security Many security-related tools use embedded encryption technologies Encryption is the process of converting an original message into a form that is unreadable by unauthorized individuals The science of encryption, known as cryptology, encompasses cryptography and cryptanalysis
  • 56. ITM 578 56 ILLINOIS INSTITUTE OF TECHNOLOGY Encryption Definitions  Algorithm: the mathematical formula used to convert an unencrypted message into an encrypted message.  Cipher: the transformation of the individual components (characters, bytes, or bits) of an unencrypted message into encrypted components.  Ciphertext or cryptogram: the unintelligible encrypted or encoded message resulting from an encryption.  Code: the transformation of the larger components (words or phrases) of an unencrypted message into encrypted components.
  • 57. ITM 578 57 ILLINOIS INSTITUTE OF TECHNOLOGY Encryption Definitions  Cryptosystem: the set of transformations necessary to convert an unencrypted message into an encrypted message.  Decipher: to decrypt or convert ciphertext to plaintext.  Encipher: to encrypt or convert plaintext to ciphertext.  Key or cryptovariable: the information used in conjunction with the algorithm to create ciphertext from plaintext.  Keyspace: the entire range of values that can possibly be used to construct an individual key.
  • 58. ITM 578 58 ILLINOIS INSTITUTE OF TECHNOLOGY Encryption Definitions  Link encryption: a series of encryptions and decryptions between a number of systems, whereby each node decrypts the message sent to it and then re-encrypts it using different keys and sends it to the next neighbor, until it reaches the final destination.  Plaintext: the original unencrypted message that is encrypted and results from successful decryption.  Steganography: the process of hiding messages in a picture or graphic.  Work factor: the amount of effort (usually in hours) required to perform cryptanalysis on an encoded message.
  • 59. ITM 578 59 ILLINOIS INSTITUTE OF TECHNOLOGY Cryptography & Encryption-Based Solutions  Simple forms of encryption are based on two concepts: the block cipher and the exclusive OR operation  With the block cipher method – the message is divided into blocks, i.e., 8 or 16 bit – and then each block is transformed using the algorithm and key  The “exclusive or operation” (XOR) is a function of Boolean algebra
  • 60. ITM 578 60 ILLINOIS INSTITUTE OF TECHNOLOGY Exclusive OR Operations Bit 1 Bit 2 Exclusive OR result 0 0 0 0 1 1 1 0 1 1 1 0 Exclusive OR OperationsTABLE 8-3
  • 61. ITM 578 61 ILLINOIS INSTITUTE OF TECHNOLOGY Encryption Algorithms  In encryption the most commonly used algorithms include two functions: substitution and transposition  In a substitution cipher, you substitute one value for another  This type of substitution is based on a monoalphabetic substitution, since it only uses one alphabet  More advanced substitution ciphers use two or more alphabets, and are referred to as polyalphabetic substitutions
  • 62. ITM 578 62 ILLINOIS INSTITUTE OF TECHNOLOGY Encryption Operations  Just like the substitution operation, the transposition cipher is simple to understand but can be complex to decipher if properly used  Unlike the substitution cipher, the transposition cipher (or permutation cipher) simply rearranges the values within a block to create the ciphertext  This can be done at the bit level or at the byte (character) level - transposition ciphers move these bits or bytes to another location in the block, so that bit 1 becomes bit 4, bit 2 becomes bit 7 etc
  • 63. ITM 578 63 ILLINOIS INSTITUTE OF TECHNOLOGY Vernam Cipher  Also known as the one-time pad, the Vernam cipher was developed at AT&T and uses a one-use set of characters, the value of which is added to the block of text  The resulting sum is then converted to text  When the two are added, if the values exceed 26, 26 is subtracted from the total (Modulo 26) - the corresponding results are then converted back to text
  • 64. ITM 578 64 ILLINOIS INSTITUTE OF TECHNOLOGY Book or Running Key Cipher  Another method, made popular by spy movies, is the use of text in a book as the algorithm to decrypt a message  The key consists of – knowing which book to use – a list of codes representing the page number, line number, and word number of the plaintext word  Dictionaries and thesauruses make the most popular sources as they guarantee every word needed, although almost any book will suffice
  • 65. ITM 578 65 ILLINOIS INSTITUTE OF TECHNOLOGY Symmetric Encryption  The same key, also known as a secret key used to conduct both encryption and decryption of the message  Can be extremely efficient, requiring minimal processing to either encrypt or decrypt the message  Problem: both sender & receiver must own the encryption key – If either copy of the key is compromised, an intermediate can decrypt and read the messages  Challenges: get copy of the key to the receiver, a process that must be conducted out-of-band to avoid interception
  • 66. ITM 578 66 ILLINOIS INSTITUTE OF TECHNOLOGY Symmetric Encryption
  • 67. ITM 578 67 ILLINOIS INSTITUTE OF TECHNOLOGY Data Encryption Standard (DES) Developed in 1977 by IBM Based on the Data Encryption Algorithm (DEA) Uses a 64-bit block size and a 56-bit key With a 56-bit key, the algorithm has 256 possible keys to choose from (over 72 quadrillion)
  • 68. ITM 578 68 ILLINOIS INSTITUTE OF TECHNOLOGY Data Encryption Standard (DES)  DES is a federally approved standard for non classified data  RSA put a bounty on the algorithm offering $10,000 to the team to crack the algorithm  Fourteen thousand users collaborated over the Internet to finally break the encryption  On 19 October 1997 at 1325 UTC, the 56 bit DES algorithm was cracked by a distributed processing system coordinated by a computer in my lab at IIT’s Main Campus
  • 69. ITM 578 69 ILLINOIS INSTITUTE OF TECHNOLOGY Triple DES (3DES)  Developed as an improvement to DES  Uses up to three keys in succession and also performs three different encryption operations: – 3DES encrypts the message three times with three different keys, the most secure level of encryption possible with 3DES  In 1998, it took a dedicated computer designed by the Electronic Freedom Frontier (www.eff.org) over 56 hours to crack DES
  • 70. ITM 578 70 ILLINOIS INSTITUTE OF TECHNOLOGY Advanced Encryption Standard (AES) The successor to 3DES is Advanced Encryption Standard (AES), based on the Rijndael Block Cipher, a block cipher with a variable block length and a key length of either128, 192, or 256 bits It would take the same computer approximately 4,698,864 quintillion years to crack AES
  • 71. ITM 578 71 ILLINOIS INSTITUTE OF TECHNOLOGY Asymmetric Encryption  Best known as public key encryption  Uses two different keys  Either key can be used to encrypt or decrypt the message, however, if Key A is used to encrypt the message, only Key B can decrypt, and if Key B is used to encrypt a message, only Key A can decrypt it.  Public key is stored in a public location, where anyone can use it  Private key is a secret known only to the owner of the key pair
  • 72. ITM 578 72 ILLINOIS INSTITUTE OF TECHNOLOGY Using Public Keys
  • 73. ITM 578 73 ILLINOIS INSTITUTE OF TECHNOLOGY Digital Signatures  An interesting thing happens when the asymmetric process is reversed, that is the private key is used to encrypt a short message  The public key can be used to decrypt it, and the fact that the message was sent by the organization that owns the private key cannot be refuted  This is known as nonrepudiation, which is the foundation of digital signatures  Digital Signatures are encrypted messages that are independently verified by a central facility (registry) as authentic
  • 74. ITM 578 74 ILLINOIS INSTITUTE OF TECHNOLOGY RSA  One of the most popular public key cryptosystems  Stands for Rivest-Shamir-Aldeman, its developers  First public key encryption algorithm developed and published for commercial use  Part of Web browsers from both Microsoft and Netscape  56 bit version is not secure; 128 bit version is acceptable
  • 75. ITM 578 75 ILLINOIS INSTITUTE OF TECHNOLOGY PKI or Public Key Infrastructure  Public Key Infrastructure is the entire set of hardware, software, and cryptosystems necessary to implement public key encryption  PKI systems are based on public-key cryptosystems and include digital certificates and certificate authorities (CAs) and can: – Issue digital certificates – Issue crypto keys – Provide tools to use crypto to secure information – Provide verification and return of certificates
  • 76. ITM 578 76 ILLINOIS INSTITUTE OF TECHNOLOGY PKI Benefits PKI protects information assets in several ways: – Authentication – Integrity – Privacy – Authorization – Nonrepudiation
  • 77. ITM 578 77 ILLINOIS INSTITUTE OF TECHNOLOGY Digital Certificates & Certificate Authorities  A digital certificate is an electronic document, similar to a digital signature, attached to a file certifying that this file is from the organization it claims to be from and has not been modified from the original format  A Certificate Authority is an agency that manages the issuance of certificates and serves as the electronic notary public to verify their worth and integrity
  • 78. ITM 578 78 ILLINOIS INSTITUTE OF TECHNOLOGY Hybrid Systems  In practice, pure asymmetric key encryption not widely used except in the area of certificates  More often used in conjunction with symmetric key encryption creating a hybrid system  Use the Diffie-Hellman Key Exchange method that uses asymmetric techniques to exchange symmetric keys to enable efficient, secure communications based on symmetric keys  Diffie-Hellman provided the foundation for subsequent developments in public key encryption
  • 79. ITM 578 79 ILLINOIS INSTITUTE OF TECHNOLOGY Hybrid Encryption Example
  • 80. ITM 578 80 ILLINOIS INSTITUTE OF TECHNOLOGY Securing E-mail  Encryption cryptosystems have been adapted to inject some degree of security into e-mail: – S/MIME builds on the Multipurpose Internet Mail Extensions (MIME) encoding format by adding encryption and authentication – Privacy Enhanced Mail (PEM) was proposed by the Internet Engineering Task Force (IETF) as a standard to function with the public key cryptosystems – PEM uses 3DES symmetric key encryption and RSA for key exchanges and digital signatures – Pretty Good Privacy (PGP), developed by Phil Zimmerman, uses the IDEA Cipher along with RSA for key exchange
  • 81. ITM 578 81 ILLINOIS INSTITUTE OF TECHNOLOGY Securing the Web Secure Electronic Transactions (SET) Secure Socket Layer (SSL) Secure Hypertext Transfer Protocol (SHTTP) Secure Shell (SSH) IPSec
  • 82. ITM 578 82 ILLINOIS INSTITUTE OF TECHNOLOGY IPSec  IP Security (IPSec) is the cryptographic authentication and encryption product of the IETF’s IP Protocol Security Working Group  Defined in RFC 1825, 1826, and 1827  Used to create Virtual Private Networks (VPNs) and is an open framework for security development within the TCP/IP family of protocol standards  Combines several different cryptosystem elements and includes: – the IP Security Protocol itself – the Internet Key Exchange
  • 83. ITM 578 83 ILLINOIS INSTITUTE OF TECHNOLOGY IPSec Operations  IPSec works in two modes of operation: – In transport mode only the IP data is encrypted, not the IP headers themselves – In tunnel mode, the entire IP packet is encrypted and is then placed as the payload in another IP packet  The implementation of these technologies is very popular through a process known as Virtual Private Networks (VPNs)  In the most common implementation, a VPN allows a user to turn the Internet into a private network between points on the public network
  • 84. ITM 578 84 ILLINOIS INSTITUTE OF TECHNOLOGY Kerberos Scenario: Initial Login
  • 85. ITM 578 85 ILLINOIS INSTITUTE OF TECHNOLOGY Kerberos Scenario: Request for Services
  • 86. ITM 578 86 ILLINOIS INSTITUTE OF TECHNOLOGY Sesame  To solve some of the problems associated with Kerberos, a new project, the Secure European System for Applications in a Multivendor Environment (SESAME), was developed as a European research and development project, partly funded by the European Commission  SESAME is similar in part to Kerberos in that the user is first authenticated to an authentication server to receive a token
  • 87. ITM 578 87 ILLINOIS INSTITUTE OF TECHNOLOGY Access Control Devices  To insure secure operation, access control needs strong authentication (two-factor authentication)  Consist of the user’s personal password or passphrase but requires at least one other factor to represent strong authentication  Frequently a physical device is used for the second factor  When considering access control you address: – What you know – What you have – Who you are – What you produce
  • 88. ITM 578 88 ILLINOIS INSTITUTE OF TECHNOLOGY What You Are - Biometrics  Most of the technologies that scan human characteristics convert these images to some form of minutiae  Minutiae are unique points of reference that are digitized and stored in an encrypted format  Each subsequent scan is also digitized and then compared with the encoded value to determine if users are who they claim to be  The problem is that some human characteristics can change over time, due to normal development, injury, or illness
  • 89. ITM 578 89 ILLINOIS INSTITUTE OF TECHNOLOGY Voice recognition Signature recognition Hand geometry Hand and palm print Fingerprint Iris recognition Retinal Recognition Facial geometry Recognition Characteristics FIGURE 8-20 Recognition Characteristics
  • 90. ITM 578 90 ILLINOIS INSTITUTE OF TECHNOLOGY Effectiveness of Biometrics Biometric technologies are evaluated on three basic criteria: –False Reject Rate –False Accept Rate –Crossover Error Rate
  • 91. ITM 578 91 ILLINOIS INSTITUTE OF TECHNOLOGY False Reject Rate (FRR) The percentage or value associated with the rate at which authentic users are denied or prevented access to authorized areas, as a result of a failure in the biometric device Type I error Probably of the least concern to security
  • 92. ITM 578 92 ILLINOIS INSTITUTE OF TECHNOLOGY False Accept Rate (FAR) The percentage or value associated with the rate at which fraudulent or non-users are allowed access to systems or areas, as a result of a failure in the biometric device Type II error This type of error is unacceptable to security, as it represents a clear breach
  • 93. ITM 578 93 ILLINOIS INSTITUTE OF TECHNOLOGY Crossover Error Rate (CER) The crossover error rate is the point at which the number of false rejections equals the false acceptances, also known as the equal error rate It is possibly the most common and important overall measure of the accuracy of a biometric system The optimal setting is somewhere near the equal error rate or CER
  • 94. ITM 578 94 ILLINOIS INSTITUTE OF TECHNOLOGY Acceptability of Biometrics While the use of one authentication area is necessary to access the system, the more devices used the better To obtain strong authentication, the systems must use two or more authentication areas
  • 95. ITM 578 95 ILLINOIS INSTITUTE OF TECHNOLOGY The End… Questions?

Editor's Notes

  1. Learning Objectives: Upon completion of this chapter you should be able to: Define and identify the various types of firewalls. Discuss the approaches to firewall implementation. Discuss the approaches to dial-up access and protection. Identify and describe the two categories of intrusion detection systems. Discuss the two strategies behind intrusion detection systems. Discuss the process of encryption and define key terms. Identify and discuss common approaches to cryptography. Compare and contrast symmetric and asymmetric encryption. Discuss various approaches to biometric access control.
  2. Learning Objectives: Upon completion of this chapter you should be able to: Define and identify the various types of firewalls. Discuss the approaches to firewall implementation. Discuss the approaches to dial-up access and protection. Identify and describe the two categories of intrusion detection systems. Discuss the two strategies behind intrusion detection systems. Discuss the process of encryption and define key terms. Identify and discuss common approaches to cryptography. Compare and contrast symmetric and asymmetric encryption. Discuss various approaches to biometric access control.
  3. Introduction Information security- A discipline that relies people, policy, education, training, awareness, procedures, and technology to improve the protection of an organization’s information assets Technical solutions can maintain Confidentiality of information Integrity of information Availability of information in each of its three states (storage, transmission, and processing).
  4. Physical Design Of The SecSDLC The physical design phase of the SecSDLC is made up of two parts: security technologies and physical security. Physical design takes the logical design, expressed by the information security blueprint and the contingency planning elements and extends the design to the next level.
  5. Physical Design Of The SecSDLC The physical design phase encompasses the selection of technologies and processes to implement controls to manage risk from threats to the information assets of the organization. At the end of the physical design phase you have: Selected technologies needed to support the information security blueprint Defined what the successful solution for a secured environment will encompass Designed physical security measures that support the technical solutions Prepared to create project plans in the implementation phase to follow
  6. Firewalls A firewall as part of an information security program is any device that prevents a specific type of information from moving between the outside world, known as the untrusted network, and the inside world, known as the trusted network, and vice versa. Firewalls have made significant advances since the earliest implementations At the present time, there are five generally recognized generations of firewalls, and these generations can be implemented in a wide variety of architectures. The firewall may be a separate computer system, a service running on an existing router or server, or a separate network containing a number of supporting devices.
  7. First Generation The first generation of firewalls are called packet filtering firewalls, because they are simple networking devices that filter packets based on their headers as they travel to and from the organization’s networks. In this case the firewall examines every incoming packet header and it can selectively filter packets (accepting or rejecting as needed) based on: address, packet type, port request and others factors. These devices scan network data packets looking for compliance with or violation of rules configured into the firewall’s database. If a first generation firewall finds a packet that matches a restriction, it simply refuses to forward it. The restrictions most commonly implemented are based on: IP source and destination address Direction (inbound or outbound) Transmission Control Protocol (TCP) or User Datagram Protocol (UDP) source and destination port-requests Early firewall models examine one aspect of the packet header: the destination and source address. They enforce address restrictions, rules designed to prohibit packets with certain addresses or partial addresses, from passing through the device. They accomplish this through access control lists (ACLs), created and modified by the firewall administrators. The ability to restrict a specific service is now considered standard in most modern routers, and is invisible to the user. Unfortunately these systems are unable to detect if packet headers have been modified, as occurs from IP spoofing attacks.
  8. Second Generation The next generation of firewalls is called the application-level firewall. The application firewall is frequently a dedicated computer separate from the filtering router and quite commonly used in conjunction with a filtering router. The application firewall is also known as a proxy server, since it runs special software designed to serve as a proxy for a service request. With this configuration the proxy server, rather than the Web server is exposed to the outside world, in the DMZ. A demilitarized zone (DMZ) is an intermediate area between a trusted network and an un-trusted network. Additional filtering routers can be implemented behind the proxy server restricting the access of internal systems to the proxy server alone, thus further protecting internal systems. The primary disadvantage of application-level firewalls is that they are designed for a specific protocol and cannot easily be reconfigured to protect against attacks on protocols for which they are not designed.
  9. Third Generation The next generation of firewalls, stateful inspection firewalls, keeps track of each network connection established between internal and external systems using a state table. These state tables track the state and context of each packet in the conversation, by recording which station sent what packet and when. Like first generation firewalls, stateful inspection firewalls perform packet filtering, but they take it a step further. Whereas simple packet filtering firewalls only allow or deny certain packets based on their address, a stateful firewall can restrict incoming packets by denying access to packets that are responses to internal requests. If the stateful firewall receives an incoming packet that it cannot match in its state table, then it defaults to its ACL to determine whether to allow the packet to pass. The primary disadvantage of this type of firewall is the additional processing requirements of managing and verifying packets against the state table. This can possibly expose the system to a DoS attack. In such an attack, the firewall can be subjected to a large number of external packets, slowing it down as it attempts to compare all of the incoming packets first to the state table and then to the ACL. On the positive side, these firewalls can track connectionless packet traffic such as UDP and remote procedure calls (RPC) traffic.
  10. Fourth Generation While static filtering firewalls, such as first and third generation, allow entire sets of one type of packet to enter in response to authorized requests, a dynamic packet filtering firewall allows only a particular packet with a particular source, destination and port address to enter through the firewall. It does this by understanding how the protocol functions, and opening and closing “doors” in the firewall, based on the information contained in the packet header. In this manner, dynamic packet filters are an intermediate form, between traditional static packet filters and application proxies.
  11. Fifth Generation The final form of firewall is the kernel proxy, a specialized form that works under the Windows NT Executive, which is the kernel of Windows NT. It evaluates packets at multiple layers of the protocol stack, by checking security in the kernel as data is passed up and down the stack.
  12. Packet-filtering Routers Most organizations with an Internet connection have some form of a router as the interface at the perimeter between the organization’s internal networks and the external service provider. Many of these routers can be configured to filter packets that the organization does not allow into the network. This is a simple but effective means to lower the organization’s risk to external attack. The drawback to this type of system includes a lack of auditing and strong authentication. The complexity of the access control lists used to filter the packets can grow and degrade network performance.
  13. Screened-Host Firewall Systems The next type of architecture combines the packet-filtering router with a separate, dedicated firewall such as an application proxy server. This approach allows the router to pre-screen packets to minimize the network traffic and load on the internal proxy. The application proxy examines an application layer protocol, such as HTTP, and performs the proxy services. This separate host is often referred to as a bastion-host, as it represents a single, rich target for external attacks, and should be very thoroughly secured.
  14. Dual-homed Host Firewalls The next step up in firewall architectural complexity is the dual-homed host. With this configuration, the bastion-host contains two NICs (network interface cards), rather than the one contained by in bastion-host configuration. One NIC is connected to the external network, and one is connected to the internal network, providing an additional layer of protection. With two NICs all traffic must physically go through the firewall to move between the internal and external networks. A technology known as network-address translation is commonly implemented with this architecture. Network-address translation (NAT) is a method of mapping real, valid, external IP addresses to special ranges of internal IP addresses, creating yet another barrier to internal intrusion. These internal addresses can consist of three different ranges.
  15. Screened-Subnet Firewalls (with DMZ) The final architecture presented here is the screened-subnet firewall. The subnet firewall consists of two or more internal bastion-hosts, behind a packet-filtering router, with each host protecting the trusted network. There are a many variants of the screened subnet architecture. The first general model consists of two filtering routers, with one or more dual-homed bastion-host between them. The second general model involves the connection from the outside or un-trusted network going through this path: Through an external filtering router Into and then out of a routing firewall to the separate network segment known as the DMZ Connections into the trusted internal network are allowed only from the DMZ bastion-host servers
  16. Provides an intermediate area between the trusted network and the untrusted network, known as a demilitarized zone (DMZ) The DMZ can be a dedicated port on the firewall device linking a single bastion-host or it can be connected to a screened subnet or DMZ Until recently, servers providing services through the un-trusted network were commonly placed in the DMZ Examples include Web, file transfer protocol (FTP), and certain database servers More recent strategies utilizing proxy servers have provided much more secure solutions
  17. SOCKS Servers The SOCKS system is a proprietary circuit-level proxy server that places special SOCKS client-side agents on each workstation. The general approach is to place the filtering requirements on the individual workstation, rather than on a single point of defense (and thus point of failure). This frees the entry router of filtering responsibilities, but then requires each workstation to be managed as a firewall detection and protection device. A SOCKS system can require additional support and management resources to configure and manage possibly hundreds of individual clients, versus a single device or set of devices.
  18. Selecting the Right Firewall 1.What type of firewall technology offers the right balance of protection features and cost for the needs of the organization? 2.What features are included in the base price? What features are available at extra cost? Are all cost factors known? 3.How easy is it to set up and configure the firewall? How accessible are staff technicians with the mastery to do it well? 4.Can the candidate firewall adapt to the growing network in the target organization? Each firewall device will have its own set of configuration rules that regulate its actions In practice the configuration of firewall policies can be something of a nightmare Simple mistakes can turn the device into a choke point In general, when security rules conflict with the performance of business, security loses since organizations are much more willing to live with a potential risk than a certain failure
  19. Each firewall device will have its own set of configuration rules that regulate its actions In practice the configuration of firewall policies can be something of a nightmare Simple mistakes can turn the device into a choke point In general, when security rules conflict with the performance of business, security loses since organizations are much more willing to live with a potential risk than a certain failure
  20. Firewall Recommended Practices All traffic from the trusted network is allowed out The firewall device is always inaccessible directly from the public network Allow Simple Mail Transport Protocol (SMTP) data to pass through your firewall, but insure it is all routed to a well-configured SMTP gateway to filter and route messaging traffic securely All Internet Control Message Protocol (ICMP) data should be denied Block telnet (terminal emulation) access to all internal servers from the public networks When Web services are offered outside the firewall, deny HTTP traffic from reaching your internal networks by using some form of proxy access or DMZ architecture
  21. Dial-Up Protection While internal network connection via private networks are now less popular due to the high cost of installation, maintenance, and protection, dial-up connections are still quite common. It is a widely held view that unsecured, dial-up access represents a substantial exposure to attack. An attacker who suspects that an organization has dial-up lines can use a device called a war-dialer to locate the connection points. Network connectivity offered by organization by using dial-up connections are usually much simpler and less sophisticated than those deployed with Internet connections. For the most part, simple username and password schemes are the only means of authentication.
  22. The RADIUS system centralizes the management of user authentication by placing the responsibility for authenticating each user in the central RADIUS server When a remote access server (RAS) receives a request for network connection from a dial-up client, it passes the request along with the user’s credentials to the RADIUS server. RADIUS then validates the credentials and passes the resulting decision (accept or deny) back to the accepting remote access server (RAS).
  23. Terminal Access Controller Access Control System The Terminal Access Controller Access Control System (TACACS) is another remote access authorization system that is based on a client/server configuration. It contains a centralized database, such as RADIUS, and validates the user’s credentials at the TACACS server. There are three versions of TACACS: TACACS, Extended TACACS, and TACACS+.
  24. Intrusion Detection Systems (IDSs) Information security intrusion detection systems (IDSs) work like a burglar alarms. When the alarm detects a violation of its configuration, it activates the alarm. As with firewall systems, IDSs require complex configurations to provide the level of detection and response desired. An IDS operates as either network-based, when the technology is focused on protecting network information assets, or host-based, when the technology is focused on protecting server or host information assets. IDSs use one of two detection methods, signature based or statistical anomaly-based. Host-based IDSs A host-based IDS resides on a particular computer or server, known as the host, and monitors activity on that system. Most host-based IDSs work on the principle of configuration or change management, in which the systems record the file sizes, locations, and other attributes, and then report when one or more of these attributes changes, when new files are created, and when existing files are deleted. A Host-based IDS can also monitor systems logs for pre-defined events. The IDS maintains its own log files; so when hackers successfully modify a systems log in an attempt to cover their tracks, the IDS provides independent verification that the attack occurred. Once properly configured, host-IDSs are very reliable. A host-based IDS that is managed can monitor multiple computers simultaneously. It does this by storing a client file on each monitored host and has that host report back to the master console, which is usually located on the systems administrator’s computer. Network-based IDSs A network-based IDS works differently than its host-based counterpart. While a host-based IDS resides on a host (or hosts) and monitors only activities on the host, a network-based IDS monitors network traffic. When a pre-defined condition occurs, a network-based IDS responds and notifies the appropriate administrator. The network IDS must match known and unknown attack strategies against its knowledge base to determine whether or not an attack has occurred. Network IDSs result in many more false positive readings than do host-based IDSs, as the system is attempting to read into the pattern of activity on the network to determine what is normal and what is not. Signature-based IDSs A signature-based IDS or knowledge-based IDS examines data traffic looking for something that matches the signatures, which are pre-configured, predetermined attack patterns. The problem with this approach is that the signatures must be continually updated, as new attack strategies are identified. If attackers are slow and methodical, they may slip undetected through the IDS, as their actions may not match the signature that includes factors based on duration of the events. Statistical Anomaly-based IDSs Another common method used in IDS is the statistical anomaly-based IDS (stat IDS) or behavior-based IDS. The stat IDS collects data from normal traffic and establishes a baseline. Once the baseline is established, the IDS periodically samples network activity, based on statistical methods, and compares the samples to the baseline. When the activity is outside the baseline parameters (known as a clipping level), the IDS then notifies the administrator. The advantage of this approach is that the system is able to detect new types of attacks, as it looks for abnormal activity of any type. Unfortunately these systems require much more overhead and processing capacity than signature-based versions, as they must constantly attempt to pattern matched activity to the baseline. These systems also may not detect minor changes to systems variables and may generate many false positives.
  25. A network-based IDS works differently than its host-based counterpart. While a host-based IDS resides on a host (or hosts) and monitors only activities on the host, a network-based IDS monitors network traffic. When a pre-defined condition occurs, a network-based IDS responds and notifies the appropriate administrator. The network IDS must match known and unknown attack strategies against its knowledge base to determine whether or not an attack has occurred. Network IDSs result in many more false positive readings than do host-based IDSs, as the system is attempting to read into the pattern of activity on the network to determine what is normal and what is not.
  26. Scanning tools are used to collect information needed by an attacker to succeed. One of the preparatory parts of an attack is the collection of information about a potential target, a process known as footprinting. Footprinting is the organized research of the Internet addresses owned or controlled by a target organization. The attacker uses public Internet data sources to perform keyword searches to identify the network addresses of the organization. This research is augmented with the browsing of the organization’s Web pages.
  27. The next phase of the pre-attack data gathering process is called fingerprinting. This is the systematic examination of all of the Internet addresses of the organization (collected during the footprinting phase noted above). Accomplished with tools discussed in the next section, fingerprinting reveals useful information for the anticipated attack
  28. Although some may not perceive them as defensive tools, scanners, sniffers, and other analysis tools are invaluable to security administrators in enabling them to see what the attacker sees. Scanner and analysis tools can find vulnerabilities in systems, holes in security components, and unsecured aspects of the network. Unfortunately, they cannot detect the unpredictable behavior of people. One word of caution though, many of these tools have distinct signatures, and some Internet service providers (ISPs) scan for these signatures. If the ISP discovers someone using hacker tools, it can pull access privileges. It’s best to establish a working relationship with the ISP and notify it of the purpose and extent of the signatures.
  29. Port Scanners Port scanning utilities (or port scanners) are tools used to identify (or fingerprint) computers that are active on a network, as well as the ports and services active on those computers, the functions and roles the machines are fulfilling, and other useful information. The more specific the scanner is, the better it can give you detailed information that will be useful later. A port is a network channel or connection point in a data communications system. Within the TCP/IP networking protocol, TCP and User Datagram Protocol (UDP) port numbers differentiate between multiple communication channels used to connect to network services being offered on the same network device. Why secure open ports? An open port can be used to send commands to a computer, gain access to a server, and exert control over a networking device. The general rule of thumb is to remove from service or secure any port not absolutely necessary for the conduct of business. If a business doesn’t host Web services, there may be no need for port 80 to be available on its servers.
  30. Vulnerability Scanners Vulnerability scanners are capable of scanning networks for very detailed information. As a class, they identify exposed usernames and groups, show open network shares, expose configuration problems, and other vulnerabilities in servers.
  31. Packet Sniffers A packet sniffer is a network tool that collects copies of packets from the network and analyzes them. It can provide a network administrator with valuable information to diagnose and resolve networking issues. In the wrong hands, a sniffer can be used to eavesdrop on the network traffic. Typically, to use these types of programs most effectively, you must be internal to a network. Simply tapping into an Internet connection floods you with more data than you can process, and technically constitutes a violation of the wiretapping act. To use a packet sniffer legally, you must be: 1) on a network that the organization owns; 2) under direct authorization of the owners of the network, and 3) have knowledge and consent of the content creators (users).
  32. Content Filters Although technically not a firewall, a content filter is a software filter that allows administrators to restrict accessible content from within a network. The most common application of a content filter is the restriction of Web sites with non-business related material, such as pornography. Another application is the restriction of spam e-mail from outside sources.
  33. Trap And Trace The trap function describes software designed to entice individuals who are illegally perusing the internal areas of a network. These individuals either discover directly or find indicators of rich content areas on the network, that turn out to be areas set up exclusively to distract potential miscreants. Better known as honey pots, these directories or servers distract the attacker while notifying the administrator. The newest accompaniment to the trap is the trace. Similar in concept to Caller ID, the trace is a process by which the organization attempts to determine the identity of someone discovered in unauthorized areas of the network or systems. If this individual turns out to be someone internal to the organization, the administrators are completely within their purview to track them down and turn them over to internal or external authorities If it turns out that the individual is outside the security perimeter, then numerous legal issues arise, as described in earlier chapters.
  34. Cryptography And Encryption-Based Solutions Although not a specific application or security tool, encryption represents a sophisticated approach to security that is implemented in many security systems. In fact, many security-related tools use embedded encryption technologies to protect sensitive information handled by the application. Encryption is the process of converting an original message into a form that is unreadable by unauthorized individuals, that is anyone without the tools to convert the encrypted message back to its original format. The science of encryption, known as cryptology encompasses cryptography, from the Greek words kryptos, meaning hidden, and graphein, meaning to write, and cryptanalysis, the process of obtaining the original message (or plaintext) from an encrypted message (or ciphertext), without the knowledge of the algorithms and keys used to perform the encryption.
  35. Encryption Definitions Algorithm: the mathematical formula used to convert an unencrypted message into an encrypted message. Cipher: the transformation of the individual components (characters, bytes or bits) of an unencrypted message into encrypted components. Ciphertext or cryptogram: the unintelligible encrypted or encoded message resulting from an encryption. Code: the transformation of the larger components (words or phrases) of an unencrypted message into encrypted components. Cryptosystem: the set of transformations necessary to convert an unencrypted message into an encrypted message. Decipher: to decrypt or convert ciphertext to plaintext. Encipher: to encrypt or convert plaintext to ciphertext.
  36. Cryptography And Encryption-Based Solutions The notation used to describe the encryption process differs depending on the source. The first uses the letters M to represent the original message, C to represent the ending ciphertext, and E to represent the encryption process: E(M) = C. This formula represents the application of encryption to a message to create ciphertext. D represents the decryption or deciphering process, thus D[E(M)]=M. K is used to represent the key, thus E(M, K) = C, or encrypting the message with the key results in the ciphertext. Now look at a simple form of encryption based on two concepts: the block cipher and the exclusive OR operation. With the block cipher method, the message is divided into blocks, i.e., 8 or 16 bit blocks, and then each block is transformed using the algorithm and key. The exclusive or operation (XOR) is a function of Boolean algebra whereby two bits are compared, and if the two bits are identical, the result is a binary 0. If the two bits are NOT the same, the result is a binary 1.
  37. Encryption Operations In encryption the most commonly used algorithms include two functions: substitution and transposition. In a substitution cipher, you substitute one value for another. This is a simple enough method by itself but very powerful if combined with other operations. This type of substitution is based on a monoalphabetic substitution, since it only uses one alphabet. More advanced substitution ciphers use two or more alphabets, and are referred to as polyalphabetic substitutions. Caesar reportedly used a three-value shift to the right giving that particular substitution cipher his name – the “Caesar Cipher. Just like the substitution operation, the transposition cipher is simple to understand but can be complex to decipher if properly used. Unlike the substitution cipher, the transposition cipher (or permutation cipher) simply rearranges the values within a block to create the ciphertext. This can be done at the bit level or at the byte (character) level. Transposition ciphers move these bits or bytes to another location in the block, so that bit 1 becomes bit 4, bit 2 becomes bit 7 etc.
  38. Vernam Cipher Also known as the one-time pad, the Vernam cipher was developed at AT&T and uses a one-use set of characters, the value of which is added to the block of text. The resulting sum is then converted to text. When the two are added, if the values exceed 26, 26 is subtracted from the total (Modulo 26). The corresponding results are then converted back to text:
  39. Book or Running Key Cipher Another method, made popular by spy movies, is the use of text in a book as the algorithm to decrypt a message. The key consists of 1) knowing which book to use, and 2) a list of codes representing the page number, line number, and word number of the plaintext word. Dictionaries and thesauruses make the most popular sources as they guarantee every word needed, although almost any book will suffice.
  40. Symmetric encryption uses the same key, also known as a secret key to conduct both the encryption and decryption of the message Symmetric encryption methods can be extremely efficient, requiring minimal processing to either encrypt or decrypt the message The problem is that both the sender and the receiver must possess the encryption key If either copy of the key is compromised, an intermediate can decrypt and read the messages One of the challenges of symmetric key encryption is getting a copy of the key to the receiver, a process that must be conducted out of band to avoid interception
  41. Symmetric Encryption There are a number of popular symmetric encryption cryptosystems. One of the most familiar is Data Encryption Standard (DES), developed in 1977 by IBM and based on the Data Encryption Algorithm (DEA). DEA uses a 64-bit block size and a 56-bit key. The algorithm begins by adding parity bits to the key (resulting in 64 bits) and then apples the key in 16 rounds of XOR, substitution, and transposition operations. With a 56 bit key, the algorithm has 256 possible keys to choose from (over 72 quadrillion). DES is a federally approved standard for nonclassified data. DES was cracked in 1997 when Rivest-Shamir-Aldeman (RSA) put a bounty on the algorithm. RSA offered a $10,000 reward for the first person or team to crack the algorithm. Fourteen thousand users collaborated over the Internet to finally break the encryption.
  42. Triple DES or 3DES Triple DES or 3DES was developed as an improvement to DES and uses up to three keys in succession. It is substantially more secure than DES, not only because it uses up to three keys to DES’s one, but because it also performs three different encryption operations as described below: 1)3DES encrypts the message with key 1, then decrypts it with key 2, and then it encrypts it with key 1 again. 2)3DES encrypts the message with key 1, then it encrypts it again with key 2, and then it encrypts it a third time with key 1 again. 3)3DES encrypts the message three times with three different keys, the most secure level of encryption possible with 3DES. Symmetric Encryption The successor to 3DES is Advanced Encryption Standard (AES), based on the Rinjndael Block Cipher, which is a block cipher with a variable block length and a key length of either128, 192, or 256 bits. In 1998, it took a special computer designed by the Electronic Freedom Frontier (www.eff.org) over 56 hours to crack DES. It would take the same computer approximately 4,698,864 quintillion years to crack AES.
  43. Another category of encryption techniques also known as public key encryption Symmetric encryption uses a single key to encrypt and decrypt but asymmetric encryption uses two different, but related keys, one public and one private If Key A is used to encrypt the message, only Key B can decrypt Public key is stored in a public location, where anyone can use it and the private key, is known only to the owner of the key pair
  44. The problem with asymmetric encryption is that it requires four keys to hold a single conversation between two parties. Asymmetric encryption is not as efficient as symmetric encryptions in terms of CPU computations. As a result, the hybrid system described in the section on Public Key Infrastructure is more commonly used, instead of a pure asymmetric system.
  45. Digital Signatures An interesting thing happens when the asymmetric process is reversed, that is the private key is used to encrypt a short message. The public key can be used to decrypt it, and the fact that the message was sent by the organization that owns the private key cannot be refuted. This is known as non-repudiation, which is the foundation of digital signatures. Digital Signatures are encrypted messages that are independently verified by a central facility (registry) as authentic.
  46. RSA One of the most popular public key cryptosystems is RSA. RSA stands for Rivest-Shamir-Aldeman, its developers. RSA is the first public key encryption algorithm developed and published for commercial use. RSA is very popular and is part of Web browsers from both Microsoft and Netscape.
  47. PKI Public Key Infrastructure is the entire set of hardware, software, and cryptosystems necessary to implement public key encryption. PKI systems are based on public-key cryptosystems and include digital certificates and certificate authorities (CAs). A common implementation of PKI includes: systems to issue digital certificates to users and servers; encryption enrollment; key issuing systems; tools for managing the key issuance; verification and return of certificates; and any other services associated with PKI.
  48. PKI protects information assets in several ways: Authentication. Digital certificates in a PKI system permit parties to validate the identity of other of the parties in an Internet transaction. Integrity. A digital certificate demonstrates that the content signed by the certificate has not been altered while being moved from server to client. Privacy. Digital certificates keep information from being intercepted during transmission over the Internet. Authorization. Digital certificates issued in a PKI environment can replace user IDs and passwords, enhance security, and reduce some of the overhead required for authorization processes and controlling access privileges. Nonrepudiation. Digital certificates can validate actions, making it less likely that customers or partners can later repudiate a digitally signed transaction.
  49. Digital Certificates and Certificate Authorities As alluded to earlier, a digital certificate is an electronic document, similar to a digital signature, attacked to a file certifying that this file is from the organization it claims to be from and has not been modified from the originating format. A Certificate Authority is an agency that manages the issuance of certificates and serves as the electronic notary public to verify their worth and integrity.
  50. Hybrid Systems In practice asymmetric key encryption is not widely used except in the area of certificates. Instead, it is more often used in conjunction with symmetric key encryption creating a hybrid system. The current process is based on the Diffie-Hellman Key Exchange method, which is a way to exchange private keys without exposure to any third parties using public key encryption. With this method asymmetric encryption is used as a method to exchange symmetric keys, so that two organizations can conduct quick, efficient, secure communications based on symmetric encryption. Diffie-Hellman provided the foundation for subsequent developments in public key encryption.
  51. Securing E-mail A number of encryption cryptosystems have been adapted in an attempt to inject some degree of security into e-mail, a notoriously unsecured medium. S/MIME builds on the Multipurpose Internet Mail Extensions (MIME) encoding format by adding encryption and authentication through digital signatures based on public key cryptosystems. Securing E-mail Privacy Enhanced Mail (PEM) was proposed by the Internet Engineering Task Force (IETF) as a standard to function with the public key cryptosystems. PEM uses 3DES symmetric key encryption and RSA for key exchanges and digital signatures. Pretty Good Privacy (PGP) was developed by Phil Zimmerman and uses the IDEA Cipher, a 128-bit symmetric key block encryption algorithm with 64 bit blocks for message encoding. IDEA performs 8 rounds on 16 bit sub-blocks using algebraic calculations. PGP also uses RSA for symmetric key exchange and for digital signatures.
  52. Securing the Web Secure Electronic Transactions (SET) was developed by MasterCard and Visa in 1997 to provide protection from electronic payment fraud. SET works by encrypting the credit card transfers with DES for encryption and RSA for key exchange, much as other algorithms do. SET provides the security for both Internet-based credit card transactions and the encryption of swipe systems of those credit cards in retail stores. Secure Socket Layer was developed by Netscape in 1994 to provide security in online electronic commerce transactions. It uses a number of algorithms, but mainly relies on RSA for key transfer and IDEA, DES or 3DES for encrypted symmetric key-based data transfer. Secure Hypertext Transfer Protocol (SHTTP) is an encrypted solution to the unsecured version of HTTP. It provides an alternative to the aforementioned protocols and can provide secure e-commerce transactions as well as encrypted Web pages for secure data transfer over the Web, using a number of different algorithms. Secure Shell (SSH) provides security over remote access connections using tunneling. It provides authentication services between a client and server. IP Security (IPSec) is the cryptographic authentication and encryption product of the IETF’s IP Protocol Security Working Group, defined in RFC 1825, 1826 and 1827. IP Security (IPSec) is used to create Virtual Private Networks (VPNs) and is an open framework for security development within the TCP/IP family of protocol standards.
  53. IPSec IPSec combines several different cryptosystems including: Diffie-Hellman key exchange for deriving key material between peers on a public network Public key cryptography for signing the Diffie-Hellman exchanges to guarantee the identity of the two parties Bulk encryption algorithms, such as DES, for encrypting the data Digital certificates signed by a certificate authority to act as digital ID cards. IPSec includes: 1) the IP Security Protocol itself, which defines the information to add to an IP packet, as well as how to encrypt packet data; and 2) the Internet Key Exchange, which uses asymmetric-based key exchange and negotiates the security associations.
  54. IPSec Operation IPSec works in two modes of operation: In transport mode only the IP data is encrypted, not the IP headers themselves. In tunnel mode, the entire IP packet is encrypted and is then placed as the payload in another IP packet. The implementation of these technologies is very popular through a process known as Virtual Private Networks (VPNs). A VPN is a network within a network. In the most common implementation, a VPN allows a user to turn the Internet into a private network. However, using the tunneling approach described earlier, an individual or organization can set up tunneling points across the Internet and send encrypted data back and forth, using the IP-packet-within-an-IP-packet method to get the data across safely and securely. VPNs are simple to set up and maintain and usually just require the tunneling points to be dual-homed, connecting a private network to the Internet or to another outside connection point.
  55. Kerberos uses symmetric key encryption to validate an individual user to various network resources Kerberos keeps a database containing the private keys of clients and servers Network services running on servers in the network register with Kerberos, as do the clients that wish to use those services The Kerberos system knows these private keys and can authenticate one network node (client or server) to another
  56. Sesame To solve some of the problems associated with Kerberos, a new project, the Secure European System for Applications in a Multi-vendor Environment (SESAME), was developed as a European research and development project, partly funded by the European Commission. SESAME is similar in part to Kerberos in that the user is first authenticated to an authentication server to receive a token.
  57. Access Control Devices There are a number of components to a successful access control physical design, the most important of which is the need for strong authentication (two-factor authentication). This authentication can consist of the user’s personal password or passphrase but requires at least one other factor to represent strong authentication. Frequently a physical device is used for the second factor. When considering access control you address: What you know: for example, passwords and pass-phrase What you have: tokens and smart cards Who you are: fingerprints, hand topography, hand geometry, retinal, and iris recognition What you produce: voice and signature pattern recognition Authentication is the validation of a user’s identity, in other words, “Are you whom you claim to be?”
  58. What You Are Most of the technologies that scan human characteristics convert these images to some form of minutiae. Minutiae are unique points of reference that are digitized and stored in an encrypted format. Each subsequent scan is also digitized and then compared with the encoded value to determine if users are who they claim to be. The problem is that some human characteristics can change over time, due to normal development, injury, or illness.
  59. Effectiveness of Biometrics Biometric technologies are evaluated on three basic criteria: False Reject Rate False Accept Rate Crossover Error Rate
  60. False Reject Rate The false reject rate is the percentage or value associated with the rate at which authentic users are denied or prevented access to authorized areas, as a result of a failure in the biometric device. This error rate is also known as a Type I error. This error rate, while a nuisance to authorized users, is probably of the least concern to security individuals.
  61. Crossover Error Rate (CER) The crossover error rate is the point at which the number of false rejections equals the false acceptances, also known as the equal error rate. It is possibly the most common and important overall measure of the accuracy of a biometric system. The optimal setting is somewhere near the equal error rate or CER.
  62. Acceptability of Biometrics While the use of one authentication area is necessary for access to the system, the more devices used the better. To obtain strong authentication, the systems must use two or more authentication areas.