Wikipedia
MediaSentry was a United States company that provided services to the music recording, motion picture, television, and software industries for locating and identifying IP addresses that are engaged in the use of online networks to share material in a manner said organizations claim is in violation of copyright. Their most notable customers were several trade associations including the Motion Picture Association of America and International Federation of the Phonographic Industry.
The company provided several services for this purpose, such as monitoring popular forums for copyright infringement, aid in litigation, early leak detection, and the distribution of decoy files. MediaSentry also monitored auction sites such as eBay for unauthorized distribution of software and other property.