Need to block single IP's from entering my server

Hello, I run a MW3 server, lately I have had trouble with hackers and I wanted something that would allow me to block there IP’s so they couldnt join my server. I have yelled and read 5 different guides, nothing I cant find anything where I can frigin put in a frigin ip and it will block it. Can someone help me out?

Always happened to me I have to write something some where in some forum asking for help then for some magical reason I all of a sudden know what Im after.

I got the IP blocking working, tested with 2 friends in my MW3 server, the server stopped showing up all togather for them in the server browser so that worked well.

What Id like to know is there a way to have only the active connections showing up in the “Active connections” screen. Under my mw3 exe file it shows whos connected to me but it also shows like 100 other connections and Im not sure why there there, my only guess it that for some reason its showing some of the other servers that are in the server browser.

I Also actiadently clicked on the “Stealth ports” option and choose to “alert me to incoming connectons and make my ports stealth on a per class basis” when I was searching for a way to block single ips. Before I clicked on this I think in active connection window it was only showing active connections which I Wanted.

Ne way thx for any help that ne one can give.