Free Riding in BitTorrent is Cheap.

While it is well-known that BitTorrent is vulnerable to selfish behavior, this paper demonstrates that even entire files can be downloaded without reciprocating at all in BitTorrent. To this end, we present BitThief, a free riding client that never contributes any real data. First, we show that simple tricks suffice in order to achieve high download rates, even in the absence of seeders. We also illustrate how peers in a swarm react to various sophisticated attacks. Moreover, our analysis reveals that sharing communities—communities originally intended to offer downloads of good quality and to promote cooperation among peers—provide many incentives to cheat. 1