Comcast, the nation's leading cable-TV and ISP provider, said on Wednesday that it will block Internet access to users who it believes have engaged in copyright infringement after it has received six complaints from copyright owners. The fifth and sixth alerts to customers trigger a 14-day appeals period in which they may appeal the impending suspension of their service to the American Arbitration Association. Users who lose their arbitration appeal or who ignore the final warning will have their Internet access cut off except for essential services like email and VOIP (online telephone services). The block will remain until the customer resolves the matter with a member of its Customer Security Assurance team. A similar plan was announced on Wednesday by Cablevision, which primarily serves the New York City area. And Verizon reinstituted its own alert system last week.