freebsd+natd+ipfw+DENY P2P

[Aleksandar Simonovski]

Hi,
i wanna allow SSH,SMTP,DNS,WWW,POP3
and nothing else :) on my freebsd gateway,
my local net is 192.168.1.0/24 and nat is working fine
the point is the deny any P2P applications, and allow normal trafic like SMTP,POP3,WWW,FTP,ICQ.
So any suggestions how to do this with ipfw and check-state,established,etc..
Just some examples or any link to them or any HOWTO's because i'm already
reading the docs but i'm lettle confused

Thank you,
Aleksandar