Underhanded C Contest

The Underhanded C Contest is in a way an opposite of the Obfuscated C Code Contest. The task is to write a readable and elegant piece of code that looks legitimate but hides a malicious feature. The feature should ideally look like an unfortunate mistake, not something intentionally added.

The contest is now back after four years of inactivity and the 2009 results are finally posted. Here is my runner-up 2009 entry.