The most efficient way to detect a hacker is turn on wall hacks (there's an admin plugin on here for it) and spec them. Almost every time you can watch them start to look at the person if not just straight stare at them through the wall. Granted the major setback is you have to physically be in the server, but if a handful of admins are always lurking around, it would fix the problem.
I know nothing about coding for cs, but if you could make it sense that the bot was being looked at through the wall, you could have a shorter time or something. That didn't come out as well as it sounded in my head. Hope you get the idea