A brief summary and information about Anti-Cheat solution for Counter-Strike: Source servers:
In this FAQ,you will be introduced to the anti-cheats available for Counter-Strike: Source servers.
Valve Anti Cheat (VAC)
This anti-cheat solution is automatically provided with your game servers, you can also disable it.
Really very little is known about this anti-cheating solution and there's a lot of speculation about its efficiency as well.
It is believed that it scans your running processes when you are connected to the game servers where VAC is enabled. Based on a small experiment with Comodo Defense +, it seems that the VAC integrated with Steam, because Steam was trying to access the memory of all running processes at regular intervals. But again, this doesn't prove anything. Basically, many people think that VAC is a huge online database of signatures comprising cheat programs.
By cons, we know that the bans are automatic and delayed (one month delay) and it is currently at version 3 (able to detect the cheat programs hidden as Windows services).
The fact that these bans are delayed pushed the anti-cheat developers to enter the field in order to more effectively protect game servers
This third site, responsible for periodically scanning each page of the Steam community, includes all banned account: http://www.vacbanned.com/.
The Anti-Cheat Staff
The Demoviewers are people responsible for viewing game records as evidence, and whether a particular player is cheating or not, to provide a banned and secure list for your servers. This is the safest method of detection, if your staff knows how to do it.
Anti-Cheat Staff - LeetGamerZ
Formerly named as clanCalendar Secure Source, the Anti-Cheat Staff from LeetGamerZ currently holds the best public banlist for CS: S.
They provides public banlist for Counter-Strike: Source, 1.6 and Condition Zero, which will help protect your server against more than 6,000 cheaters.
An interesting and comprehensive project developed by the alliedmodders.net community.
Contains two simple anti-aimbot, Wallhack blocker, RadarHack blocker, ConVar Bypass detector, Bunnyhop and AutoPistol script detector, anti-spam protection and a simple rcon access.
To conclude, if you really want to avoid any form of cheating on your server, I recommend you to install instant DBlocker and NoCheatZ 3 Beta because they are complementary (Anti-Aimbot + Anti-Wallhack) then activate the VAC and put sv_pure 2.