This is interesting and not unconnected. It explains some of the details behind the recent Linux hack.

Basically, code was hidden in an image type file and it acted in concert with the software building/compiling software to insert a number of "back doors" into open source software. Many eyes would have seen the code but no-one could see what was happening.

It was not until someone started to do performance checks on his computer that it was realised that the computer was spending time on some unknown tasks.