Comprehensive Computer Network Security Course

1. Computer Security Instructor: Dr. Bo Sun

2. Course Objectives • Understand basic issues, concepts, principles, and mechanisms in computer network security • Basic security concept • Cryptography • Authentication • Standards • Network Security

3. Course Outline • Basic Security Concepts: • Confidentiality, integrity, availability • others • Cryptography • Secret Key Cryptography: DES, IDEA, AES, etc. • Public Key Cryptography: RSA, Diffi-Hellman, Digital signature, Elliptic Curve, etc. • Modes of Operation: ECB, CBC etc. • Hashes and Message Digests: MD5, SHA-1 etc. • Authentication • Basic concepts of Authentication Systems • Password Authentication • Security handshake pitfalls

4. Course Outline cont’d • Network and Distributed Systems • Kerberos • Public Key Infrastructure • IPsec • SSL/TLS • Email security • Firewall

5. Introduction

6. Security Attacks

7. Security Attacks

8. Classify Security Attacks as • passive attacks - eavesdropping on, or monitoring of, transmissions to: • obtain message contents, or • monitor traffic flows • active attacks – modification of data stream to: • masquerade of one entity as some other: man-in-the-middle • replay previous messages • modify messages in transit • denial of service

9. Information Security Concerns • DDoS • Worm Attacks (e.g. code red) • Exploitation of software bugs (e.g. buffer overflow) • Monitoring and capture of network traffic • Masquerade of authorized users • ……. • http://www.cert.org/

10. Contributing Factors • Lack of awareness of threats and risks of information systems • Wide-open network policies • Many Internet sites allow wide-open Internet access • Vast majority of network traffic is unencrypted • Lack of security in TCP/IP • Complexity of security management and administration • Exploitation of software bugs: e.g. Sendmail bugs • Cracker skills keep improving

11. Security Objectives Confidentiality (Secrecy): Prevent/Detect/Deter improper disclosure of information Availability:Prevent/Detect/Deter improper denial of access to services provided by the system Integrity:Prevent/Detect/Deter improper modification of information

12. Security Mechanisms Access Control

13. Security Services • Confidentiality: protection of any information from being exposed to unintended entities. • Information content • Parties involved • Where they are, how they communicate, how often, etc. • Authentication: assurance that an entity of concern or the origin of a communication is authentic - it’s what it claims to be or from • Integrity: assurance that the information has not been tampered with

14. Security Services • Non-repudiation: offer of evidence that a party is indeed the sender or a receiver of certain information • Access control: facilities to determine and enforce who is allowed access to what resources, hosts, software, network connections • Security management: facilities for coordinating users’ service requirements and mechanism implementations throughout the enterprise network and across the internet – Trust model – Trust communication protocol – Trust management infrastructure

15. OSI of ISO Internet Stack Application Presentation Upper Layers Session Transport Transport Network Internet Data Link Data Link Physical Physical TheInternet

16. Layered Store-and-forward User A User B Application Transport Network Link

17. Virus, Worms, and Trojan Horses • Trojan horse: instructions hidden inside an otherwise useful program that do bad things • Virus: a set of instructions that, when executed, inserts copies of itself into other programs. • Worm: a program that replicates itself by installing copies of itself on other machines across a network. • Trapdoor: an undocumented entry point, which can be exploited as a security flaw • Zombie: malicious instructions installed on a system that can be remotely triggered to carry out some attack with les traceability because the attack comes from another victim. • ….