I found this
http://lists.evolt.org/archive/Week-of- ... 19180.html
what you want to do with this file is. add the line
xxx.xxx.xxx.xxx 127.0.0.1
where xxx.xxx.xxx.xxx is the ip address of each cheater you wish to ban.
What this file does is, when ever someone on this list tries to contact your computer. it will redirect the output back to 127.0.0.1 ( your local computer ) when the they do not get a reply, their computer thinks your computer is not on line any more.
Real all the other threads after this one as they talk more about this format and how it works on a mac.
Hope this helps.