's social networking site announced Friday that it's launching Take Down Stay Down, a program designed to filter videos uploaded by users for copyrighted materials.
The social networking site has used another copyright filtering program called Audible Magic since February to pick out copyrighted videos based on their "digital fingerprint, " a pattern of pitches in the video's audio track.
File-exchange sites like Gnutella and Hotline, which act as matchmakers for people who want to exchange movies and other copyrighted material, aren't nearly as easy to use as the popular music-exchange program Napster.