PeerGuardian is a tiny IP blocker program especially designed for all P2P software users, but also to anyone who is concerned about their privacy on the internet.
PeerGurdian blocks connections for the configured IP ranges and logs the blocked connections. It acts as an incoming firewall for specific IP addresses. It uses blocklists for the blocking, but IP ranges can also be configured manually. Pre-configured for blocking are RIAA, MPAA and many others. The SafePeer plugin for Azureus uses a subset of the PeerGuardian blocklists, which can be quite extensive if you elect to use all of them.
A supplementary program called BlocklistManager can automate the task of keeping the lists up to date.