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CIT 380: Securing Computer Systems

CIT 380: Securing Computer Systems. Security Solutions Part 2. Assumptions. Security rests on assumptions specific to type of security required and environment. Assumptions. Example: TCP/IP designed for pre-commercial Internet. Assumed only legitimate administrators had root access.

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CIT 380: Securing Computer Systems

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

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

  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

  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. CIT 380: Securing Computer Systems

  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. CIT 380: Securing Computer Systems

  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

  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. CIT 380: Securing Computer Systems

  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. References • Ross Anderson, Security Engineering, Wiley, 2001. • Matt Bishop, Introduction to Computer Security, Addison-Wesley, 2005. • Peter Neumann, (moderator), Risks Digest, http://catless.ncl.ac.uk/Risks/ • Bruce Schneier, Beyond Fear, Copernicus Books, 2003. • 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/) CIT 380: Securing Computer Systems

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