Computer security
New to topics? Read the documentation here!
As mentioned at Section "Computer security researcher", Ciro Santilli really tends to like people from this area.
Also, the type of programming Ciro used to do, systems programming, is particularly useful to security researchers, e.g. Linux Kernel Module Cheat.
The reason he does not go into this is that Ciro would rather fight against the more eternal laws of physics rather than with some typo some dude at Apple did last week and which will be patched in a month.