Hackers I Admire

These are the people who wrote C. C is C. Often described, with a mixture of fondness and disdain varying according to the speaker, as "a language that combines all the elegance and power of assembly language with all the readability and maintainability of assembly language". In his Reflections on Trusting Trust Ken Thompson said "I am a programmer. On my 1040 form, that is what I put down as my occupation.". He had also written a very cunning Trojan Horse into the C compiler which he describes in his essay. I will give it briefly here:

The C compiler contained code that would recognize when the `login' command was being recompiled and insert some code recognizing a password chosen by Thompson, giving him entry to the system whether or not an account had been created for him. Normally such a back door could be removed by removing it from the source code for the compiler and recompiling the compiler. But to recompile the compiler, you have to use the compiler -- so Thompson also arranged that the compiler would recognize when it was compiling a version of itself, and insert into the recompiled compiler the code to insert into the recompiled `login' the code to allow Thompson entry -- and, of course, the code to recognize itself and do the whole thing again the next time around! And having done this once, he was then able to recompile the compiler from the original sources; the hack perpetuated itself invisibly, leaving the back door in place and active but with no trace in the sources.