A Conversation for C - the Programming Language

Recursive virus

Post 1

some bloke who tried to think of a short, catchy, pithy name and spent five sleepless nights trying but couldn't think of one

I think I've been told that one of the people writing the original C compiler for one system put a virus in it which would compile a bit of extra code into the programs it created. There was also a failsafe so that this code was reintroduced if you tried to recompile the C compiler.


Recursive virus

Post 2

Hal

It was Ken Thompson (the inventor of UNIX).
The C compiler source code was first modified so it would recognize when it was a compiling a version of the UNIX login program, and insert code so that a particular password was always accepted.

This would still be visible in the source files for the compiler itself. Threfore code was inserted into the compiler so when it was compiling -itself-, it would insert code that would later insert code into the login compilation.

The compiler was then compiled, and traces of the back-door taken out of the compiler source code... and so all systems would recognize Ken's password, but no system administrators could know such a back-door existed.

It became public knowledge in the early '80s.


Recursive virus

Post 3

some bloke who tried to think of a short, catchy, pithy name and spent five sleepless nights trying but couldn't think of one

Yep. That's the one. It was a year or so ago that I heard that so I'd forgotten a lot of it.


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