When Ken Thompson won the Turing Award jointly with Dennis Ritchie for their work in UNIX, he was expected like other Turing winners to write a paper that would be published in the ACM Computer Journal. What he ended up submitting was a paper about "the cutest program [he] ever wrote"-- a sneaky undetectable self-reproducing "Trojan horse" backdoor in the C compiler that would allow him to log into affected machines as any user.