We definitely need some webpage to link people with such questions. In a nutshell there is no solution to all kinds of attacks. Considering you have linux, it is easier for you to work with iptables. But as I understand you still don't have quite useful anti-cheat which also takes care of many server-side exploits.
http://forums.alliedmods.net/forumdisplay.php?f=133
No one can give you a promise that any kind of program they advice will solve issue of someone being able to lag your server, if they do - they lie.