Hi,
I have made a server-side anti-cheat module for ioquake3. A brief description of the module can be found here:
http://linradiant.intron-trans.hu/anticheat.html
The source code and prebuilt binaries for Linux and Windows (both 32-bit) can be downloaded here:
http://linradiant.intron-trans.hu/ioq3-ac-src.zip
http://linradiant.intron-trans.hu/ioq3-ac-bin.zip
This is an alpha release for testing. At this time only wallhack prevention is implemented. Please, get the stuff, try it and tell me what you think.