In August, Comcast denied accusations that it was purposely disrupting file-sharing among its customers, but reports of stymied traffic — particularly from people using the popular BitTorrent protocol — have continued.

Late last week, The Associated Press reported (news.yahoo.com) that Comcast "actively interferes with attempts by some of its high-speed Internet subscribers to share files online." Peter Svensson of The A.P. wrote that the practice was "the most drastic example yet of data discrimination by a U.S. Internet service provider."

This week, the company told Brad Stone of The New York Times in a statement that it "does not block access" to any applications, but that it does "use the latest technologies to manage our network" to ensure quality of service to its customers (bits.blogs.nytimes.com).

But an anonymous Comcast executive admitted that in some cases peer-to-peer file-sharing traffic like that generated by BitTorrent, is delayed, though not blocked. But Dave Burstein, the editor of DSL Prime, is among those not persuaded. "Comcast has definitely been blocking BitTorrent in some circumstances," he wrote (dslprime.com).

The AP confirmed the interference by conducting nationwide tests of Comcast's network. "If widely applied by other I.S.P.'s," Mr. Svensson said, the practice could strike "a crippling blow to the BitTorrent, eDonkey and Gnutella file-sharing networks."

BitTorrent, though still often used for illicit sharing of copyrighted material, is increasingly used by media companies to distribute legitimate files.

But copyrights are not Comcast's concern in this case — bandwidth is. Its interference "appears to be an aggressive way of managing its network to keep file-sharing traffic from swallowing too much bandwidth and affecting the Internet speeds of other subscribers," Mr. Svensson wrote.

The practice plays into the debate over "net neutrality" — whether Internet service providers should be allowed to choose which traffic they carry. "Not only does the company have a major P.R. disaster on its hands, but it has in a matter of days become the poster child for net neutrality," wrote Chris Soghoian of CNET (cnet.com).

Lawyers "are circling the water," Mr. Soghoian wrote. "They can smell blood."