How are DMCA notices different from Copyright Alerts?

How are DMCA notices different from Copyright Alerts?

Comcast now operates two methods of responding to claims of alleged copyright infringement by our subscribers. Our Digital Millennium Copyright Act (DMCA) response policy continues to notify subscribers by email and US mail regarding allegations of infringement. Our new Copyright Alerts program sends alerts in response to notices generated by certain content owners who have a good faith belief that an IP address linked to one of our subscribers has used a peer to peer file sharing program (P2P or more generally FSP) to download and/or make available for upload movies, television programs, music or other works in a way they believe infringes their copyrights. The Copyright Alerts System is designed so you cannot receive more than one alert in a seven day period. The DMCA program has no such limitation.