First off let me say I do not condone copyright infringement but I am big on security and privacy. This app offers that, so that is why I am mentioning it. PeerGuardian 2 is not fool proof but it does offer decent protection of your P2P privacy. To me, what you download (legally of course) in the privacy of your own home is your business and yours alone!
Basically this app is a running blacklist that is continuously being updated of networks that you do not want connecting to your home network. When one of these blacklisted networks tries to connect to your home network, PeerGuardian 2 simply drops that those packets and moves on.
Like mentioned before it is not fool proof, if one of those blacklisted networks changes it’s external network IP address and this new IP address has not been added to the blacklist yet. Then you run the chance of this network being able to connect to your home network.
All-in-all I would recommend this app because any security is better than no security. Unfortunately right now, there is no better or easier way of protect your privacy. Also did I mention that it is open source, got to love open source!