For years, antipiracy companies like MediaDefender (read our 2007 profile) have scratched out a living by flooding peer-to-peer file-sharing networks with bad data. While the techniques differ, the goal is the same: to make online piracy just enough of a hassle that legal alternatives look good by comparison.

This attempt at poisoning the P2P well started a quiet war between the file-swappers and the antipiracy groups, each escalating the arms race by rolling out new weapons and new countermeasures. File-swappers began blocking known IP ranges that served fake files, and sites like The Pirate Bay worked to remove bad links to fake content and to ban the user accounts of those who uploaded the listing information.

And yet, despite years of this sort of sniping, P2P networks remain flooded with fake files. New research suggests that nearly a third of the files at big BitTorrent trackers are bogus.

A group of European academics, most of them from Universidad Carlos III de Madrid, presented a paper (PDF) at an Association of Computing Machinery (ACM) conference last month in Philadelphia that tries to quantify the motives of the biggest BitTorrent seeders. Most seeders turn out to have less-than-altruistic motives, instead using their uploads to advertise faster private trackers or advertising-funded websites. But one major group of seeders had a different economic incentive: making money from record labels and movie companies for disrupting P2P networks.

A huge dataset from popular BitTorrent search engines The Pirate Bay and Mininova showed that antipiracy agencies managed to upload an amazing 30 percent of all files in the study group (which comprised 55,000 top files shared by 35 million IP addresses). And these files weren't simply ignored by users; even taking the countermeasures deployed by search sites and their users into account, fake files made up 25 percent of actual user downloads.

Poisoning the well

The paper concludes that "major BitTorrent portals are suffering from a systematic poisoning index attack that affects 30 percent of the published content.

As for the effectiveness of countermeasures: "The portals fight this phenomenon by removing the fake content as well as the user accounts used to publish them. However, contrary to what has been reported in previous studies, this technique does not seem to be sufficiently effective since millions of users initiate the download of fake content."

Not all of these fake publishers are antipiracy groups; some are just criminals. The two dominant categories of content from the "fake publishers" are movies and software—in fact, the "fake publishers" upload more software than any other group. The study's authors conclude that most of the video content from fake publishers comes from antipiracy groups, but that the software is more likely to be from malicious users out to spread a computer virus or promote a botnet.

Compared to legitimate files, the fake files are unpopular—for obvious reasons—and so are not redistributed by many users. That means the fake publishers need to stay connected for long periods of time to fully seed their files. Researchers found, in fact, that they spend the most time connected "due to their obligation to continuously seed their content to keep it alive." And most of these fake connections come from only three Web hosts: tzulo, FDC Servers and 4RWEB.

Still, this "unpopularity" is relative. The antipirates have managed to make one out of every four downloads from The Pirate Bay an unsatisfying experience—which must be quite satisfying indeed to those paid to cause this sort of confusion.