I'm plenty familiar with the Halting Problem for Turing Machines. It occurred to me after reading several posts on this site that it would be interesting, educational and useful to start a list of equivalents to the Halting Problem in terms of Computer Security. I think this might help students of computer science and allied areas come to appreciate the true depth and application of the Halting Problem in whatever their application area.
So, I ask that the proposed (or actual) equivalent problem be:
(1) One that makes sense in the domain of computer security. This can be from information management, Cryptography, hacking, or programming (ideally with a security bent, since there are plenty of Halting equivalent problems already well known in the world of programming languages and compilers).
(2) One stated with a reference to literature on that subject if possible, and maybe even (although I wouldn't require it) a proof if you know of an elegant one.
Example: I have an antivirus software on my machine, and I want to know whether it will ever execute malicious code. As far as I can tell, this is the Halting problem in disguise.