Researchers from the Max Planck Institute for Software Systems tested BitTorrent blocking by ISPs around the world. Of 1,224 ISPs measured, 13 were found to block out BitTorrent traffic. Of those 13, nine were located in the United States.
According to an Ars Technica report, Comcast and Cox were, far and away, the most aggressive. Both blocked more than half of attempted BitTorrent tests on their networks. Cox blocked 82 of 151 tests, while Comcast blocked 491 of 788 tests.
Singapore, Malaysia, Canada and Ireland each had one ISP that engaged in BitTorrent blocking, researchers said.
While Comcast representatives have admitted to monitoring and managing traffic flow to BitTorrent sites, particularly during peak traffic times, the research shows Comcast and Cox were found to block consistently throughout the day.
Comcast currently is facing a civil class-action suit in San Francisco for blocking peer-to-peer traffic.
Ben Scott, policy director for Free Press, one of the groups pressuring the Federal Communications Commission to take action in the proceedings involving Comcast, responded to researchers' findings with a statement.
"Consumers have no reason left to trust their cable company," he said. "These Internet experts have also unequivocally demonstrated that blocking is not limited to times of supposed congestion. Their sophisticated testing shows that Comcast and Cox block BitTorrent applications at all times of the day, not just at times of peak traffic.
"This research proves beyond a shadow of a doubt that consumers, Congress and the FCC must urgently pursue the complaints against network providers."
Comcast also responded to the report.
"Comcast does not, has not and will not block any websites or online applications, including peer-to-peer services like BitTorrent," Comcast said. "We have acknowledged that we manage peer-to-peer traffic in a limited manner to minimize network congestion. While we believe our current network management approach was a reasonable choice, we are now working with a variety of companies, including BitTorrent, and confirm our March announcement that we will move to a protocol-agnostic network management technique no later than Dec. 31, 2008."