Pls anyone can help me to block yahoo messenger where i'm using Redhat Linux 7.3, i'm badly needed this set of rules in order to block YM or any equivalent application. I'm using Linux as router for my 2 internal or private network (all client machine running MS windows)to connect them on internet or single public IP. Pls help me. Thanks everybody, hoping to resolve my problem ASAP.

# iptables -A INPUT -p tcp --dport 5050 -j drop will drop Yahoo Messenger # iptables -A INPUT -p tcp --dport 1863 -j drop will drop MS Messenger I think the above are correct. NB These uses iptables, so you must have a 2.4.X kernel with firewalling etc enabled.