Let me dial the paranoia up a little by calling your attention to this historic text:

http://www.ece.cmu.edu/~ganger/712.fall02/papers/p761-thomps...

A quote from the conclusions:

"In demonstrating the possibility of this kind of attack, I picked on the C compiler/ I could have picked on any program-handling program such as an assembler, a loader, or even hardware microcode. As the level of program gets lower, these bugs will be harder and harder to detect. A well-installed microcode bug will be almost impossible to detect."