I'm a fanatic of Murphy's Law and I have it in mind at programming time. There are a lot of "applied" versions in a variety of fields. Maybe (as stack overflow users) we can compile a list of them applied to Internet Security. I suggest this because in times of phishing, XSS, CSRF and a lot more of treats surrounding the programmer and the users it would be a good idea to have a list of what to expect in order to keep track of possible vulnerabilities in your apps and systems.
An example would be: "Vulnerabilities appears spontaneously but they don't disappear in the same way".
Please show your ideas about it. Thanks in advance.
The only truly secure system is one that is powered off, cast in a block of concrete and sealed in a lead-lined room with armed guards - and even then I have my doubts.
-- Eugene H. Spafford