Introduction to Computer Security

1. Introduction to Computer Security Dr. ShahriarBijani Shahed University

2. Slide References • Matt Bishop, Computer Security: Art and Science, the author homepage, 2004. • Michael E. Whitman, Principles of Information Security: Chapter 1: Introduction to Information Security, 4/e, 2011. • Chris Clifton, CS 526: Information Security course, Purdue university, 2010. • Patrick Traynor, CS 8803 - Cellular and Mobile Network Security, Georgia Tec, 2012.

3. What is Security? Security /sɪˈkjʊərɪti/ noun • the state of being free from danger or threat. • synonyms: certainty, safe future, assured future, safety, reliability, dependability, solidness, soundness

4. What is Security? • A successful organization should have multiple layers of security in place: • Physical security: to protect the physical items, objects, or areas of an organization from unauthorized access and misuse. • Personal security: to protect the (group of) authorized individual. • Operations security: to protect the details of a particular operation or series of activities. • Communications security: to protect an organization’s communications media, technology, and content. • Network security: to protect networking components, connections, and contents. • Information security

5. Basic Components • An Information System is secure if it supports CIA: • Confidentiality • Keeping data and resources hidden • Integrity • Data integrity (integrity) • Origin integrity (authentication) • Availability • Enabling access to data and resources The CIA triangle

6. The History of Information Security • Began immediately following development first mainframes • Developed for code-breaking computations • During World War II • Multiple levels of security were implemented • Physical controls • Elementary • Mainly composed of simple document classification • Defending against physical theft, espionage, and sabotage

7. The 1960s • Original communication by mailing tapes • Advanced Research Project Agency (ARPA) • Examined feasibility of networked communications • Larry Roberts developed ARPANET • Plan • Link computers • Resource sharing • Link 17 Computer Research Centers • Cost 3.4M $ • ARPANET is predecessor to the Internet

8. The 1970s and 80s • ARPANET grew in popularity • Potential for misuse grew • Fundamental problems with ARPANET security • Individual remote sites were not secure from unauthorized users • Vulnerability of password structure and formats • No safety procedures for dial-up connections to ARPANET • Non-existent user identification and authorization to system

9. The 1970s and 80s‏ … • Rand Report R-609 • Paper that started the study of computer security • Information Security as we know it began‏ • Scope of computer security grew from physical security to include: • Safety of data • Limiting unauthorized access to data • Involvement of personnel from multiple levels of an organization

10. The 1990s • Networks of computers became more common • Need to interconnect networks grew • Internet became first demonstration of a global network of networks • Initially based on de-facto standards • In early Internet deployments, security was treated as a low priority

11. 2000 to Present • Millions of computer networks communicate • Many of the communication unsecured • Ability to secure a computer’s data influenced by the security of every computer to which it is connected • Growing threat of cyber attacks has increased the need for improved security

12. Challenges of computer security • Computer security is not simple • One must consider potential (unexpected) attacks • Must decide where to deploy mechanisms • Involve algorithms and secret info (keys) • A battle between attacker / admin • It is not perceived on benefit until fails • Requires constant monitoring • Too often incorporated after the design is complete (not integral) • Regarded as a barrier to using system

13. Key Information Security Concepts • Access • Adversary • Asset • Attack • Control, Safeguard, or Countermeasure • Exploit • Exposure • Hack • Loss • Nonrepudiation • Subjects / Objects • Risk • Threat • Vulnerability

14. Relationships of Security Concepts

15. Key Information Security Concepts • Computer can be subject or object of an attack • When the subject of an attack • An active tool to conduct attack • When the object of an attack • An entity being attacked Source: Principles of Information Security, 4th Edition

16. Information Security vs. Access • Perfect security is impossible • Security is a process • Security should be considered balance between protection and availability • Must allow reasonable access, yet protect against threats

17. Information Security vs. Access Source: Principles of Information Security, 4th Edition

18. Vulnerabilities Principles of Information Security, 4/e

19. Threats • A threat is a potential violation of security.

20. Classes of Threats • Interruption (Disruption) • interruption or prevention of correct operation • DOS attack: Denial of Service • Interception / Disclosure • Unauthorized access to information • Snooping: the unauthorized interception of information • Modification • An unauthorized party not only gains access to but modify an asset. • Masquerading or spoofing: an impersonation of one entity by another. • Fabrication • An unauthorized party inserts fake objects into the system.

21. Classes of Threats

22. Examples of threats

23. Adversary • An adversary is anyone attempting to bypass the security infrastructure. • The curious and generally inexperienced (e.g., script-kiddies) • Unintended attackers seeing to understand systems • Malicious and terrorist groups • Competitors (industrial espionage) • Governments

24. Attack • An attack occurs when someone attempts to exploit a vulnerability • Type of attacks • Passive (e.g., eavesdropping) • Active (e.g., password guessing, DoS) • A compromise occurs when an attack is successful

25. Trust • Trust • The degree to which an entity is expected to behave. • Trust is a particular level of the subjective probability with which an agent assesses that another agent will perform a particular action in a context that affects his actions [Gambetta, 1990] • Reputation • Expectation about an entity’s behavior based on past behavior [Abdul-Rahman, 2000] • May be used to determine trust

26. Trust Management • Trust Management as a countermeasure: • Trust relationships between peers help establish confidence • Two types of trust management systems • Credential and Policy-based • Reputation-based

27. Security Model • A security model is the combination of a trust and threat models that address the: • set of perceived risks • The “security requirements” used to develop some cogent and comprehensive design • Every design must have security model • LAN network or global information system? Java applet or operating system? • The single biggest mistake seen in use of security is the lack of a coherent • security model • It is very hard to retrofit security (design time) • This class is going to talk a lot about security models • What are the security concerns (risks)? Threats? • Who are our adversaries? • Who do we trust and to do what? • Systems must be explicit about these things to be secure

28. Policies and Mechanisms • Policy says what is, and is not, allowed • This defines “security” for the site/system/etc. • Mechanisms enforce policies • Composition of policies • If policies conflict, inconsistencies may create security vulnerabilities

29. Trust and Assumptions • Underlie all aspects of security • Policies • Unambiguously partition system states • Correctly capture security requirements • Mechanisms • Assumed to enforce policy • Support mechanisms work correctly

30. Goals of Security • Prevention(پیشگیری) • Prevent attackers from violating security policy • Detection (تشخیص) • Detect attackers’ violation of security policy • Recovery(ترمیم) • Stop attack, assess and repair damage • Continue to function correctly even if attack succeeds