blocking specific ips on a linux server

[Meghan Madel <megmadel mac com>]

Hello,
I would like to block AIM on a linux server.  What would you recommend 
is the best way to do this.  I found some documentation on 
"access-lists," but am not familiar with this. I couldn't tell if it 
was it's own file or if this was to be added to another file.

I have found info on the ip's, port #, etc.....just don't know where or 
how to block those.

Any suggestions would be appreciated.

Thanks,
Meghan