NEW YORK — Comcast Corp. actively interferes with attempts by some of its high-speed Internet subscribers to share files online, a move that runs counter to the tradition of treating all types of Net traffic equally. The interference, which The Associated Press confirmed through nationwide tests, is the most drastic example yet of data discrimination by a U.S. Internet service provider. It involves company computers masquerading as those of its users. If widely applied by other ISPs, the technology Comcast is using would be a crippling blow to the BitTorrent, eDonkey and Gnutella file-sharing networks. While these are mainly known as sources of copyright music, software and movies, BitTorrent in particular is emerging as a legitimate tool for quickly disseminating legal content. The principle of equal treatment of traffic, called ‘Net Neutrality’ by proponents, is not enshrined in law but supported by some regulations. Most of the debate around the issue has centered on tentative plans, now postponed, by large Internet carriers to offer preferential treatment of traffic from certain content providers for a fee. Comcast’s interference, on the other hand, appears to be an aggressive way of managing its network to keep file-sharing traffic from […]