You can’t trust Ken Thompson. He’ll prove it. Reflections on Trusting Trust Ken Thompson created the modern world. When he was given the Turning award in 1984 for that small accomplishment he gave a small speech that proves that you can’t trust him. At all. It’s a simple three step proof. If a compiler has a backdoor that infects programs, we’ll only find the hack by reading the source code of the compiler. Compilers are compiled by a programming language, just like any other program. If the compiler has a backdoor that infects a compiler, we cannot find hack by reading the source code, not after it has been bootstrapped. It’s a beautiful little paper that will make you question the whole notion of security. ...

It shouldn’t be surprising to anyone that New York taxes were managed by a handful of programmers. But most programmers would be scared to learn how much of it was done in Perl.