The Copyright Alert System (CAS) is a U.S. anti-piracy strategy designed and implemented in 2011 by the Center for Copyright Information (CCI). Under this system, content owners, with the Motion Picture Association of America (MPAA) and Recording Industry Association of America (RIAA) serving as representatives, share details, preferably IP addresses, of subscribers that conduct illegal file sharing with Internet Service Providers (ISP). The ISPs then investigate and possibly take measures against offending subscribers.

On discovery of a suspected copyright infringement, the IP address linked with the suspect activity is forwarded to the associated ISP. The ISP then notifies the claimed infringement’s subscriber of the IP address suspected of copyright violation. The ISP also warns the subscriber of probable infringement consequences. Users that continue copyright infringement, even after a warning, may receive a maximum of six alerts as email or pop-up messages from their ISP prior to being subjected to stronger sanctions.