Comcast and Cox are blocking BitTorrent traffic, regardless of the time of day or day of the week, students from the Max Planck Institute for Software Systems report. And despite suggestions that BitTorrent blocking is widespread across ISPs, the Institute's Glasnost test found that the two cable networks accounted for vast majority of BitTorrent blocking in the U.S.
Most (573 of 599) U.S. hosts that observed blocking are located in Comcast and Cox networks. In Singapore, all blocked hosts are connected using the StarHub network. While we did observe blocking for hosts in 10 other ISPs (7 of which are in the U.S.), we did not see widespread blocking of BitTorrent traffic for hosts in those ISPs.
The table below shows the details of BitTorrent blocking for Comcast, Cox, and StarHub. For each ISP, we show (a) the number of distinct hosts we measured, and (b) the number of these hosts for which we detected BitTorrent blocking.
ISP Country # measured
Comcast USA 788 491 Cox USA 151 82 StarHub Singapore 45 26
And despite Comcast's claims that blocking only occurs to deal with network congestion:
The percentage of blocked connections remains high at all times of the day. Our data suggests that the BitTorrent blocking is independent of the time of the day.