Copyright Alert System

The Copyright Alert System (CAS) is a private system for alerting, educating, and punishing subscribers of five major Internet service providers in the United States of America, based on accusations of the use of BitTorrent and peer-to-peer file sharing to infringe the copyrights of certain entertainment corporations by distributing, without authorization, those companies' intellectual property. The press has branded the CAS as a "six strikes" program. The participating Internet service providers (ISPs) are AT&T, Cablevision, Time Warner Cable, Verizon and Comcast.

The CAS is intended to be a graduated response system wherein participating ISPs send up to six electronic warnings notifying subscribers of alleged copyright infringement, as reported by a monitoring service working on behalf of participating copyright owners. If copyright infringement is reported after a final warning, the ISPs have agreed to implement "mitigation measures", which can include penalties such as bandwidth throttling or preventing web access until customers "discuss the matter" with their ISP.

The CAS framework was established on July 7, 2011 by the Center for Copyright Information (CCI), after 3 years in the making. After multiple delays, ISPs began implementing it in late February 2013.

The Center for Copyright Information employs the services of MarkMonitor (often doing business as DtecNet) to detect and monitor suspected copyright infringement activity. Although MarkMonitor monitors many infringement venues, in early 2013 the Electronic Frontier Foundation (EFF) said it appears that for purposes of the CAS, the company will only monitor peer-to-peer traffic from public BitTorrent trackers. The Copyright Alert System does not use deep packet inspection.

...
Wikipedia