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Anonymising Bittorrent code could be its downfall

If reports are to be believed
Fri Apr 16 2010, 15:36

A FEW LINES OF CODE thought to be capable of making Bittorrent anonymous is in fact just the thing copyrights holders might be looking for.

Reports surfaced of a 85 line bit of code which apparently could be modified to make Bittorrent downloads anonymous does, in fact, poison torrents. The script, merely a proof of concept, creates ficitious nodes to join a torrent and participate in a swarm.

Depending on the implementation of this code those fake nodes could be used to send fake 'pieces' to unwitting clients. The coder claims that users on "broadband connections" can create up to "a thousand fake peers in less than 5 minutes".

The idea of torrent poisoning is pretty attractive to those who want to undermine the Bittorrent protocol. A number of firms, including the infamous Mediadefender, employ such tactics in order to introduce 'noise' within the swarm, meaning that downloaders end up with incomplete files. There are, unsurprisingly, several ways to avoid this with the simplest being limiting the range of Bittorrent clients able to receive a list of nodes participating in the swarm.

Modifying Bittorrent clients such as the open source 'Mainline' client originally developed by protocol designer Bram Cohen, is pretty common. Many researchers modify clients in order to observe and measure swarm activity for papers while others modify clients to report, falsely, download and upload amounts in order to keep favourable 'ratios' on private tracker sites. It is particularly the second reason that has lead to many trackers to ban all but a few clients.

For those who really want to stay anonymous, probably the best way is to use Tor, an onion routing system. However using Tor for anything other than Web browsing goes against its self imposed ettiquette. Of course Bittorrent isn't the only way to obtain files on the Internet with Usenet remaining popular. With rentable anonymous VPN and SSL Usenet accounts easily available, having some resemblence of anonymity while taking part in downloading dodgy content can be achieved.

As for the offending code, the potiental for it to be used to have a negative effect on Bittorrent swarms clearly exists but as research by Dhungel et al [1] shows, Bittorrent is a fairly resiliant protocol, as we're sure Mediadefender has found out. µ

[1] Dhungel, P. and Wu, D. and Ross, K.W. Measurement and mitigation of BitTorrent leecher attacks. In Computer Communications, 2009


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