The document discusses the OSI security architecture and common network security threats and defenses. It begins with an introduction to the OSI security architecture proposed by ITU-T as a standard for defining and providing security across network layers. It then discusses (1) specific security mechanisms like encryption and digital signatures and pervasive mechanisms like security audits; (2) common passive and active security threats like eavesdropping and denial of service attacks; and (3) that passive attacks focus on prevention while active attacks require detection and recovery. It concludes with exercises asking about these topics.

1. Inam Ul Haq
MS Computer Science (Sweden)
Inam.bth@gmail.com, mr.inam.ulhaq@ieee.org
Discussion forum: questions.computingcage.com
Member of IEEE, ACM, Movement Disorder Society, PDF, BossMedia,
Michealjfox, Association for Information Systems and Internet Society.
Network Security
1 Network Security, University of Okara
Lecture 3: OSI Security Architecture

2. Table of Contents
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 OSI Security Architecture
 4 Common Attacks
 Handling Attacks
 Exercise

3. OSI Security Architecture
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 An international and systematic standard of
defining and providing security requirements.
 Used by IT managers and vendors in their
products
 Proposed by ITU-T in recommendations X.800
as “Security Architecture for OSI”
 security attack
 security mechanism (control)
 A process (or a device incorporating such a process) that is
designed to detect, prevent, or recover from a security attack.
 security service
 enhances the security of the data processing systems and the
information transfers of an organization

4. Security Mechanisms (X.800)
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 Specific Security Mechanisms:
 encipherment, digital signatures, access controls, data
integrity, authentication exchange, traffic padding,
routing control, notarization
 Pervasive Security Mechanisms:
 trusted functionality, security labels, event detection,
security audit trails, security recovery

5. 4 Common Types of Threats
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6. Network Security, University of Okara6
4 Common Types of Threats (2)

7. Handling Attacks
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 Passive attacks – focus on Prevention
 Easy to stop
 Hard to detect
 Active attacks – focus on Detection and
Recovery
 Hard to stop
 Easy to detect

8. Exercise
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1. What is the OSI security architecture?
2. What is the difference between passive and active
security threats?
3. List and briefly define categories of passive and
active security attacks.
4. List and briefly define categories of security
services.
5. List and briefly define categories of security
mechanisms.