1. CIT 380: Securing Computer Systems Security Solutions Part 2

2. CIT 380: Securing Computer Systems Slide #2 Assumptions Security rests on assumptions specific to type of security required and environment.

3. Assumptions Example: – TCP/IP designed for pre-commercial Internet. Assumed only legitimate administrators had root access. Trusted IP addresses, since only root can set IP address. What happens to network when Windows 95 systems added to network, where desktop user has all privileges? CIT 380: Securing Computer Systems Slide #3

4. CIT 380: Securing Computer Systems Slide #4 Assurance How much can you trust a system? Example: – Purchasing aspirin from a drugstore. – Bases for trust: Certification of drug by FDA. Reputation of manufacturer. Safety seal on bottle.

5. CIT 380: Securing Computer Systems Slide #5 How much do you trust? Ken Thompson’s compiler hack from “Reflections on Trusting Trust.” – Modified C compiler does two things: If compiling a compiler, inserts the self-replicating code into the executable of the new compiler. If compiling login, inserts code to allow a backdoor password.

6. How much do you trust? – After recompiling and installing old C compiler: Source code for Trojan horse does not appear anywhere in login or C compiler. Only method of finding Trojan is analyzing binary. CIT 380: Securing Computer Systems Slide #6

7. CIT 380: Securing Computer Systems Slide #7 Key Points Components of security – Confidentiality – Integrity – Availability States of information – Storage, Processing, Transmission Evaluating risk and security solutions. – Security is a matter of trade-offs. Security is a human problem.

8. Discussion: Gas Drive Away Without Paying What measures can be imposed? What are the costs for the merchant and the customer? Do the benefits outweigh the costs?

9. CIT 380: Securing Computer Systems Slide #9 References 1.Ross Anderson, Security Engineering, Wiley, 2001. 2.Matt Bishop, Introduction to Computer Security, Addison-Wesley, 2005. 3.Peter Neumann, (moderator), Risks Digest, http://catless.ncl.ac.uk/Risks/ 4.Bruce Schneier, Beyond Fear, Copernicus Books, 2003. 5.Ken Thompson, “Reflections on Trusting Trust”, Communication of the ACM, Vol. 27, No. 8, August 1984, pp. 761-763 ( http://www.acm.org/classics/sep95/)