Does anyone knows which port that messenger used?like msn or yahoo messanger. And which property that i should set the firewall filter rule to block someone cannot chatting using msn or yahoo messanger? sorry,i'm newbie in mikrotik n networking. Thanx for ur help...

Here is a list of Ports used and common applications including chat and messenger programs.

http://www.practicallynetworked.com/sha ... t_list.htm

Example: (Yahoo Messenger Chat)
/ip firewall filter add chain=forward dst-port=5000-5001 protocol=tcp action=drop