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Jim Louderback, the CEO of Revision3, is jumpin' mad. A denial-of-service attack brought down the online-video network over the weekend, and it wasn't the work of a freelance hacker with a distributed network of compromised machines, he writes in the company blog. It was, he says, the deliberate act of MediaDefender, an antipiracy consulting group which works to shut down file-sharing networks. Revision3 uses BitTorrent, a file-sharing protocol, to distribute its own content, and runs a "tracker" server to coordinate those downloads. All of this is quite legal. MediaDefender, it turns out, found a security hole in Revision3's server, and planted unknown files, possibly illegal copies on Revision3's servers, for their own purposes. It's not clear why, but whatever the motive, MediaDefender may have broken several laws in doing so.

What brought down Revision3's network wasn't the security hole, however. It was MediaDefender's response after Revision3 technicians noticed the breach and shut it down. MediaDefender's servers, in what that company told Louderback was an automated response, started trying to contact Revision3's servers through the now-closed hole. That turned into a flood of traffic that overwhelmed Revision3's network.

MediaDefender has worked for Sony Music, the Recording Industry Association of America, and the Motion Picture Association of America to shut down illegal file-sharing networks. But Revision3's use of file sharing for its own content was entirely legal; to the extent its servers pointed to any illegal files, it was only because of MediaDefender's hacking, Louderback tells me.

Revision3 has asked the FBI to investigate MediaDefender's alleged abuses. For years, the music and movie industries have been telling us that sharing files is criminal, and that blocking file-sharing networks is proper. For millions of file-sharing users, it would be quite satisfying to see the opposite proved in court.