How to block bittorrent??
well it depends on your bittorrent version:
But you add begin with blocking tcp 6881 and TCP 6969 with the firewall - source and dest.
Create rules for just the traffic you want to leave your network on the LAN interface, then remove the default allow rule. We can't kill BT totally at this point, but that should sufficiently cripple it (assuming that "normal" web browsing is all you need).
In my experience blocking 6881-6999 will help in most cases. A more effective solution involves squid. Look at one of the squid threads for my suggestion of this feature.