P2P applications are file sharing programs that are designed to let people easily exchange music, movies, video and other files over the Internet. Some common programs are Ares, BitTorrent, KaZaa and LimeWire.
P2P file sharing is not, itself, unlawful. It's what is being shared using peer-to-peer networks that that may or may not be lawful. There are legitimate and lawful uses of peer-to-peer networks. Unfortunately, there are also illegal uses of those networks.
Copyright law protects creative work. If you download or share copyrighted material without the copyright holder's consent, you are breaking the law. Peer-to-peer programs make lawbreaking easy—so easy it might not seem illegal at all. Of course, if you get sued or arrested, the courts won't care that it didn't seem like you were doing anything wrong. The only course of action you should take is to avoid violating copyrights.
When you purchasing a work (e.g., a song or a movie) it gives you the right to view, listen to, or play the work but does not allow for the distribution of that work. If you "rip" your CDs to your computer/MP3 player, or purchase and download a work online, be sure to take steps to ensure that it is not being shared [see links for reconfiguring P2P applications in the right hand column].
You are responsible for your computer and everything that takes place on it. Use caution when lending your computer to others. You should also take necessary steps to ensure your operating system has the latest updates, patches, and virus software.
There are a number of legal download services, including the following: