This document discusses tools for identifying network vulnerabilities. It describes common categories of vulnerabilities like defects in software/firmware and weaknesses in processes/procedures. Various scanning and analysis tools are outlined that can detect these vulnerabilities, including port scanners, firewall analysis tools, OS detection tools, vulnerability scanners, and packet sniffers. Regularly using these tools helps network administrators identify and address vulnerabilities before attackers can exploit them.

1. FIREWALLS & NETWORK SECURITY with
Intrusion Detection and VPNs, 2nd ed.
4
Finding Network Vulnerabilities
By Whitman, Mattord, & Austin © 2008 Course Technology

2. Learning Objectives
 Name the common categories of vulnerabilities
 Discuss common system and network
vulnerabilities
 Locate and access sources of information about
emerging vulnerabilities
 Identify the names and functions of the widely
available scanning and analysis tools
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 2

3. Introduction
 To maintain secure networks, information security
professionals must be prepared to identify system
vulnerabilities, whether by hiring system
assessment experts or by conducting self-
assessments using scanning and penetration
tools
 Network security vulnerability is defect in product,
process, or procedure that, if exploited, may
result in violation of security policy, which in turn
might lead to loss of revenue, loss of information,
or loss of value to the organization
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 3

4. Common Vulnerabilities
Common vulnerabilities fall into two broad
classes:
 Defects in software or firmware
 Weaknesses in processes and procedures
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 4

5. Defects in Software or Firmware
 Buffer overruns (or buffer overflows) arise when
quantity of input data exceeds size of available
data area (buffer)
 Injection attacks can occur when programmer
does not properly validate user input and allows
an attacker to include input that, when passed
to a database, can give rise to SQL injection
vulnerabilities
 Network traffic is vulnerable to eavesdropping
because a network medium is essentially an
open channel
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 5

6. Defects in Software or Firmware
(continued)
 How can security professionals remain abreast
of all the vulnerabilities?
 First and perhaps foremost, they must know:
– Organization’s security policies
– Software and hardware the organization uses
 Information security professionals should
regularly consult these public disclosure lists:
– Vendor announcements
– Full disclosure mailing lists
– CVE: the common vulnerabilities and exposures
database
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 6

7. Vendor Announcements
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 7

8. BugTraq
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 8

9. Weaknesses in Processes and
Procedures
 Just as hazardous as software vulnerabilities
 More difficult to detect and fix because they
typically involve the human element
 Often arise when policy is violated or processes
and procedures that implement policy are
inadequate or fail
 To ensure security policy is implemented,
organizations should hold regular security
awareness training and regularly review policies
and their implementation
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 9

10. Scanning and Analysis Tools
 To truly assess risk within computing
environment, technical controls must be
deployed using strategy of defense in depth
 Scanners and analysis tools can find
vulnerabilities in systems, holes in security
components, and unsecured aspects of the
network
 Scanners, sniffers, and other such vulnerability
analysis tools are invaluable because they
enable administrators to see what attackers see
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 10

11. Scanning and Analysis Tools
(continued)
 Scanning tools are typically used as part of an
attack protocol
 Attack protocol is a series of steps or processes
used by attacker, in logical sequence, to launch
attack against target system or network
 This may begin with a collection of publicly
available information about a potential target, a
process known as footprinting
 Attacker uses public Internet data sources to
perform searches to identify network addresses
of the organization
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 11

12. Footprinting
 Most important information for footprinting
purposes is IP address range
 Another piece of useful information is name,
phone number, and e-mail address of the
technical contact
 This research is augmented by browsing the
organization’s Web pages since Web pages
usually contain information about internal
systems, individuals developing Web pages,
and other tidbits, which can be used for social
engineering attacks
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 12

13. Footprinting (continued)
 To assist in footprint intelligence collection
process, an enhanced Web scanner can be
used that, among other things, can scan entire
Web sites for valuable pieces of information,
such as server names and e-mail addresses
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 13

14. Sam Spade
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 14

15. Fingerprinting
 Next phase of attack protocol is data-gathering
process called fingerprinting, a systematic
survey of all of the target organization’s Internet
addresses that is conducted to identify network
services offered by hosts in that range
 Fingerprinting reveals useful information about
internal structure and operational nature of the
target system or network
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 15

16. Port Scanners
 Port scanning utilities (port scanners) are tools
used by both attackers and defenders to identify
computers that are active on a network, as well
as ports and services active on those
computers, functions and roles the machines
are fulfilling, and other useful information
 The more specific the scanner is, the better and
more useful the information it provides is, but a
generic, broad-based scanner can help locate
and identify rogue nodes on the network
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 16

17. Port Scanners (continued)
 Port is a network channel or connection point in a
data communications system
 Within TCP/IP, TCP and UDP port numbers
differentiate multiple communication channels
used to connect to network services being offered
on same device
 In all, there are 65,536 port numbers in use for
TCP and another 65,536 port numbers for UDP
 Ports greater than 1023 typically referred to as
ephemeral ports and may be randomly allocated
to server and client processes
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 17

18. Port Scanners (continued)
 Why secure open ports?
 Open port is an open door and can be used by
attacker to send commands to a computer,
potentially gain access to a server, and possibly
exert control over a networking device
 The general policy statement is to remove from
service or secure any port not absolutely
necessary to conducting business
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 18

19. Firewall Analysis Tools
 Understanding exactly where organization’s
firewall is located and what existing rule sets do
are very important steps for any security
administrator
 Several tools that automate remote discovery of
firewall rules and assist administrator (or
attacker) in analyzing rules to determine exactly
what they allow and what they reject
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 19

20. Firewall Analysis Tools (continued)
 Administrators wary of using same tools
attackers use should remember:
– Regardless of the nature of the tool used to
validate or analyze firewall’s configuration, it is
the intent of the user that dictates how
information gathered will be used
– To defend a computer or network, it is necessary
to understand ways it can be attacked; thus, a
tool that can help close up an open or poorly
configured firewall helps network defender
minimize risk from attack
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 20

21. Operating System Detection Tools
 Identifying target computer’s operating system is
very valuable to attacker
 Once the operating system is known, it is easy to
determine all vulnerabilities to which it might be
susceptible
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 21

22. Vulnerability Scanners
 Passive vulnerability scanner listens in on the
network and identifies vulnerable versions of
both server and client software
 Active vulnerability scanners scan networks for
highly detailed information by initiating network
traffic in order to identify security holes
– These scanners identify exposed usernames and
groups, show open network shares, and expose
configuration problems and other vulnerabilities
in servers
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 22

23. Vulnerability Scanners (continued)
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 23

24. Vulnerability Validation
 Often, an organization requires proof that
system is actually vulnerable to certain attacks
 May require such proof to avoid having system
administrators attempt to repair systems that
are not broken or because they have not yet
built satisfactory relationship with vulnerability
assessment team
 Class of scanners exists that exploit remote
machine and allow vulnerability analyst
(penetration tester) to create accounts, modify
Web pages, or view data
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 24

25. Vulnerability Validation (continued)
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 25

26. Packet Sniffers
 Network tool that collects copies of packets from
network and analyzes them
 Sometimes called a network protocol analyzer
 Can provide network administrator with valuable
information for diagnosing and resolving
networking issues
 In the wrong hands, sniffer can be used to
eavesdrop on network traffic
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 26

27. Packet Sniffers (continued)
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 27

28. Wireless Security Tools
 Wireless connection, while convenient, has
many potential security holes
 Security professional must assess risk of
wireless networks
 Wireless security toolkit should include ability to
sniff wireless traffic, scan wireless hosts, and
assess level of privacy or confidentiality
afforded on wireless network
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 28

29. Wireless Security Tools (continued)
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 29

30. Penetration Testing
 Penetration test involves using all techniques
and tools available to attacker in order to
attempt to compromise or penetrate an
organization’s defenses
 Penetration testing can be performed by internal
group (so called “red teams”) or outsourced to
external organization
 A variable of the penetration test, whether
performed internally or outsourced, is amount of
information provided to the red team
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 30

31. Penetration Testing (continued)
 Three categories of testing:
– Black box: red team is given no information
whatsoever about the organization and
approaches the organization as external attacker
– Gray box: red team is given some general
information about the organization such as
general structure, network address ranges,
software and versions
– White box: red team has full information on the
organization and its structure
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 31

32. Chapter Summary
 To maintain secure networks, information
security professionals must be prepared to
systematically identify system vulnerabilities
 Often done by performing self-assessment
using scanning and penetration tools testing
 Common vulnerabilities fall into two classes:
– Defects in software or firmware
– Weaknesses in processes and procedures
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 32

33. Chapter Summary (continued)
 Information security professionals should
regularly consult vendor announcements, full
disclosure mailing lists, and the common
vulnerabilities and exposures (CVE) database
 To assess risk within a computing environment,
network professionals must use tools such as
intrusion detection systems (IDPS), active
vulnerability scanners, passive vulnerability
scanners, automated log analyzers, and
protocol analyzers (sniffers)
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 33

34. Chapter Summary (continued)
 Many organizations use penetration test to
assess their security posture on a regular basis
 Penetration test team (red team) uses all
techniques and tools available to attackers in
order to attempt to compromise or penetrate an
organization’s defenses
Firewalls & Network Security, 2nd ed. - Chapter 4 Slide 34