David Downs of the SF Weekly invited Electronic Frontier Foundation spokeshacker Peter Eckersly into his home to test claims that Comcast is blocking BitTorrent files:

Eckersley's BitTorrent controller flickers for a second, showing that his computer is "seeding" our file to the Melbourne computer. Then everything stops. The transmission fails, and to an untrained eye, the problem appears to be with BitTorrent.

But Eckersley is running a Net monitor application called Wireshark, which works like an online customs officer checking the packets going out of the computer here and into the one in Melbourne. What Eckersley finds is damning. Someone or something has interceded in the transmission and told the computers to stop talking.

And that something, experts have concluded, is Comcast.

The experiment Eckersley and I ran replicates private and public versions that emerged last fall through an Associated Press story. That story confirmed what many in software circles knew for most of 2007: Comcast has been looking at its users' Web traffic and secretly blocking some of the Internet, namely BitTorrent uploads, to users outside Comcast's network. The Electronic Frontier Foundation alleges that Comcast blocks BitTorrent with a classic hacker technique called "spoofing," where the hacker poses as someone he isn't, in this case another user. Eckersley describes it as if he and I were having a phone conversation, and then halfway through Comcast interrupts us and in my voice tells him to hang up, and in his voice tells me the same thing.