Anti-cheat technologies?

Tek7 (Legacy)

CGA & ToJ President
I'm a bit tired, so I'll keep this brief. Heh.

What anti-cheat technology works best to keep hackers out of Natural Selection servers? Please post links where appropriate.

I'd like to have some kind of anti-cheat measure installed before we "officially" launch the server.
I didn't know there was cheating/anti-cheat tech for NS. Figured that all the script kiddies flocked to CS only.