1. (DUE October 4, 2005 by midnight EDT) Briefly discuss what you learned from the readings in chapters 12-13:
   • What was the most surprising thing you learned?
   • What was the most difficult part for you?
2. (DUE October 4, 2005 by midnight EDT) Select one of the following questions to discuss in detail through the threaded discussion.
   • A common technique for inhibiting password guessing is to disable an account after three consecutive failed login attempts.
     
     1. Discuss how this technique might prevent legitimate users from accessing the system. Why is this action a violation of the principle of least common mechanism?
     2. One can argue that this is an example of fail-safe defaults, because by blocking access to an account under attack, the system is defaulting to a known, safe state. Do you agree or disagree with this argument? Justify your answer.
   • Kernighan and Plauger [506] argue a minimalist philosophy of tool building. Their thesis is that each program should perform exactly one task, and more complex programs should be formed by combining simpler programs. Discuss how this philospohy fits in with the principle of economy of mechanism. In particular, how does the advantage of the simplicity of each component of a software system offset the disadvantage of a multiplicity of interfaces among the various components?
   • Given that the Internet is a shared network, discuss whether preventing denial of service attacks is inherently possible or not possible. Do systems connected to the Internet violate the principle of least common mechanism?
3. (DUE Oct. 9, 2005 by midnight EDT) Select a discussion from one or more of your classmates and respond to their comments.

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