Block Yahoo Messenger, AOL, MSN and ICQ using IPTABLES

If you’re a network administrator and you’re using Linux on your servers, you can stop the rest of the users from using IM applications by blocking their access to the most-used IM protocols:
ICQ and AOL:
# iptables -A FORWARD –dport 5190 -j DROP

# iptables -A FORWARD -d login.oscar.aol.com -j DR

OP
MSN:
# iptables -A FORWARD -p TCP –dport 1863 -j DROP

# iptables -A FORWARD -d 64.4.13.0/24 -j DROP

Yahoo Messenger:
# iptables -A FORWARD -p TCP –dport 5000:5010 -j REJECT

# iptables -A FORWARD -d cs.yahoo.com -j REJECT
# iptables -A FORWARD -b scsa.yahoo.com -j REJECT