Better for security

1. Computer Security
(week - 1)
(CoSc4171 – 3CrHr/5ECTS)
Semester I – 2015 E.C
Shegaw M. (ethioprogramming1@gmail.com)

2. Computer Security
“The
most secure
computers are those
not connected
to the Internet and
shielded
from any interference”

3. Computer Security
Computer security is about provisions
and policies adopted to protect
information and property from theft,
corruption, or natural disaster while
allowing the information and property to
remain accessible and productive to its
intended users.
Computer security is the protection afforded to an automated
information system in order to attain the applicable objectives of
preserving the integrity, availability, and confidentiality of information
system resources (includes hardware, software, firmware,
information/data, and telecommunications).

4. Computer Security
Network security deals with provisions and policies adopted
to prevent and monitor unauthorized access, misuse,
modification, or denial of the computer network and network
accessible resources.
Internet

5. Computer Security/Goals
Security Goals
Integrity
Confidentiality
Availaibility

6. Computer Security/ Goals
Confidentiality: Preserving authorized restrictions on information
access and disclosure, including means for protecting personal
privacy and proprietary information. A loss of confidentiality is the
unauthorized disclosure of information.
Integrity: Guarding against improper information modification or
destruction, including ensuring information nonrepudiation and
authenticity.
A loss of integrity is the unauthorized modification or destruction
of information
Availability: Ensuring timely and reliable access to and use of
information.
A loss of availability is the disruption of access to or use of
information or an information system.

7. Computer Security/ Overview
Security: The prevention and protection of an assets from
unauthorized access, use, alteration, degradation, destruction, and
other threats.
Privacy: The right of the individual to be protected against
intrusion into his personal life or affairs, or those of his family, by
direct physical means or by publication of information.
Security/Privacy Threat: Any person, act, or object that poses a
danger to computer security/privacy. Threat is a possible danger
that might exploit a vulnerability.
Attack is an assault on system security that derives from an
intelligent threat; that is, an intelligent act that is a deliberate
attempt (especially in the sense of a method or technique) to evade
security services and violate the security policy of a system.

8. Computer Security/ Overview
Countermeasure is an action, device, procedure, or technique that
reduces a threat, a vulnerability, or an attack by eliminating or
preventing it, by minimizing the harm it can cause, or by
discovering and reporting it so that corrective action can be taken.
Risk An expectation of loss expressed as the probability that a
particular threat will exploit a particular vulnerability with a
particular harmful result.
Security Policy is a set of rules and practices that specify or
regulate how a system or organization provides security services to
protect sensitive and critical system resources.
Vulnerability - A flaw or weakness in a system’s design,
implementation, or operation and management that could be
exploited to violate the system’s security policy.

9. Computer Security and Privacy/ Attacks
Interruption: An attack on availability
Interception: An attack on confidentiality
Modification: An attack on integrity
Fabrication: An attack on authenticity
Categories of Attacks

10. Computer Security and Privacy/Attacks
Categories of Attacks/Threats (W. Stallings)
Normal flow of information
Interruption Interception
Modification Fabrication
Source
Destination
Attack

11. Computer Security and Privacy/ Vulnerabilities
Physical vulnerabilities (Ex. Buildings)
Natural vulnerabilities (Ex. Earthquake)
Hardware and Software vulnerabilities (Ex. Failures)
Media vulnerabilities (Ex. Disks can be stolen)
Communication vulnerabilities (Ex. Wires can be tapped)
Human vulnerabilities (Ex. Insiders)
Types of Vulnerabilities

12. Computer Security and Privacy/ Countermeasures
Computer security controls
 Authentication (Password, Cards, Biometrics)
 Encryption
 Auditing
 Administrative procedures
 Standards
 Certifications
 Physical Security
 Laws

13. Computer Security and Privacy
Physical Security

14. Computer Security and Privacy/ Physical Security
Physical security is the use of physical controls to protect
premises, site, facility, building or other physical asset of an
organization [Lawrence Fennelly]
Physical security protects your physical computer facility (your
building, your computer room, your computer, your disks
and other media) [Chuck Easttom].

15. Computer Security and Privacy/ Physical Security
In the early days of computing physical security was simple
because computers were big, standalone, expensive machines
₯ It is almost impossible to move them (not portable)
₯ They were very few and it is affordable to spend on
physical security for them
₯ Management was willing to spend money
₯ Everybody understands and accepts that there is
restriction

16. Computer Security and Privacy/ Physical Security
Today
₯ Computers are more and more portable (PC, laptop, PDA,
Smartphone)
₯ There are too many of them to have good physical security
for each of them
₯ They are not “too expensive” to justify spending more
money on physical security until a major crisis occurs
₯ Users don’t accept restrictions easily
₯ Accessories (ex. Network components) are not considered
as important for security until there is a problem
₯ Access to a single computer may endanger many more
computers connected through a network

17. Computer Security and Privacy/ Physical Security
Natural Disasters
 Fire and smoke
 Fire can occur anywhere
 Solution – Minimize risk
Good policies: NO SMOKING, etc..
Fire extinguisher, good procedure and training
Fireproof cases (and other techniques) for backup tapes
Fireproof doors
 Climate
 Heat
 Direct sun
 Humidity
Threats and vulnerabilities

18. Computer Security and Privacy/ Physical Security
Natural Disasters …
 Hurricane, storm, cyclone
 Earthquakes
 Water
 Flooding can occur even when a water tab is not properly closed
 Electric supply
 Voltage fluctuation
Solution: Voltage regulator
 Lightning
Threats and vulnerabilities …
Solution
 Avoid having servers in areas often hit by Natural Disasters!

19. Computer Security and Privacy/ Physical Security
People
Intruders
 Thieves
 People who have been given access unintentionally by the
insiders
 Employees, contractors, etc. who have access to the facilities
 External thieves
 Portable computing devices can be stolen outside the
organization’s premises
Loss of a computing device
Mainly laptop
Threats and vulnerabilities …

20. Computer Security and Privacy/ Physical Security
Safe area
Safe area often is a locked place where only
authorized personnel can have access using
Surveillance/guards, video-surveillance, automatic-doors
with security code locks, alarms, etc.
Organizations usually have safe area for keeping
computers and related devices

21. Computer Security and Privacy/ Attacks & Threats
Computer Security - Attacks and
Threats

22. Computer security/ Attacks & Threats
A computer security threat is any person, act, or
object that poses a danger to computer security
Computer world is full of threats!
And so is the real world!
Thieves, pick-pockets, burglars, murderers,
drunk drivers, …

23. Computer security/ Attacks & Threats
What do you do in real life?
 You learn about the threats
 What are the threats
 How can these threats affect you
 What is the risk for you to be attacked by these threats
 How you can protect yourself from these risks
 How much does the protection cost
 What you can do to limit the damage in case you are attacked
 How you can recover in case you are attacked
 Then, you protect yourself in order to limit the risk but to
continue to live your life
You need to do exactly the same thing with computers!

24. Computer security/ Types of Attacks & Threats
Hacking Attack:
 Any attempt to gain unauthorized access to your system.
Denial of Service (DoS) Attack
 Blocking access from legitimate users
Physical Attack:
 Stealing, breaking or damaging of computing devices
Malware Attack:
 A generic term for software that has malicious purpose
 Examples: Viruses, Trojan horses, Spy-wares, worm
New ones: Spam/scam, identity theft, e-payment frauds, etc.

25. Computer security/ Types of Attacks & Threats
Viruses
 “A small program that replicates and hides itself inside other
programs usually without your knowledge.” Symantec
 Similar to biological virus: Replicates and Spreads
Worms
 An independent program that reproduces by copying itself from one
computer to another
 It can do as much harm as a virus
 It often creates denial of service
Trojan horses
 Secretly downloading a virus or some other type of mal-ware on to
your computers.
Spy-wares
 “A software that literally spies on what you do on your computer.”
 Example: Simple Cookies and Key Loggers

26. Computer security/Threats
Functions of anti-viruses
₯ Identification of known viruses
₯ Detection of suspected viruses
₯ Blocking of possible viruses
₯ Disinfection of infected objects
₯ Deletion and overwriting of infected objects
Anti-Virus …

27. Computer Security/ OSI Security Architecture
The OSI Security Architecture
1. Security attack: Any action that compromises the
security of information owned by an organization.
2. Security mechanism: A process (or a device
incorporating such a process) that is designed to detect,
prevent, or recover from a security attack.
3. Security service: A processing or communication
service that enhances the security of the data processing
systems and the information transfers of an organization.

28. OSI Security Architecture/Security attacks
A useful means of classifying security attacks is in terms of
passive attacks and active attacks.
A passive attack attempts to learn or make use of
information from the system but does not affect system
resources.
® Two types of passive attacks are the release of message
contents and traffic analysis.
1. Release of message contents - e.g., from a telephone conversation,
e-mail, transferred files, etc.
2. Traffic analysis - e.g., location and identity of communicating
hosts, frequency and length of messages, the nature of messages.

29. OSI Security Architecture/Security attacks
An active attack attempts to alter system resources or affect their
operation.
Active attacks can be subdivided into four categories: masquerade,
replay, modification of messages, and denial of service.
© A masquerade takes place when one entity pretends to be a different
entity.
© Replay involves the passive capture of a data unit and its subsequent
retransmission to produce an unauthorized effect.
© Modification of messages simply means that some portion of a
legitimate message is altered, or that messages are delayed or
reordered, to produce an unauthorized effect.
© The denial of service prevents or inhibits the normal use or
management of communications facilities.

30. OSI Security Architecture/Security Services
Security Services divides these services into five categories or services.

31. OSI Security Architecture/Security Services
₯ The function of the authentication service is to assure the recipient that
the message is from the source that it claims to be from.
₡ the service assures that the two entities are authentic
₡ service must assure that the connection is not interfered
This authentication service can be peer entity or data entity authentication.
₯ Access control is the ability to limit and control the access to host
systems and applications via communications links.
₯ Confidentiality is the protection of transmitted data from passive attacks.
₯ Integrity can be connection-oriented or connectionless
₵ A connection-oriented integrity service deals with a stream of messages
and assures that messages are received as sent with no duplication,
insertion, modification, reordering, or replays.

32. OSI Security Architecture/Security Services
₵ A connectionless integrity service deals with individual
messages without regard to any larger context and generally
provides protection against message modification only.
₯ Nonrepudiation prevents either sender or receiver from denying a
transmitted message.
A Prove the sent & received message B
₯ Availability to be the property of a system or a system resource
being accessible and usable upon demand by an authorized
system entity.
₵ This service addresses the security concerns raised by
denial-of-service attacks.

33. OSI Security Architecture/Security Mechanism
₵ The mechanisms are divided into specific and pervasive security mechanisms:

34. Q & C
What are the challenges of computer security?