Modeling Leechers attack in BitTorrent

As one of the most widely-used Peer-to-Peer applications, BitTorrent system has gained a lot of successes in last decade. BitTorrent has been extensively studied in the literature. However, few research studies vulnerabilities of BitTorrent, and the abuses of BitTorrent have already impeded the wide adoption of the system. In this paper, we study a common attack on BitTorrent - the Leechers attack, which tries to take over valid connections of legitimate users without paying for them. It is harmful to a swarm if certain percentage of users perform the selfish behavior. We present an analytical model for the Leechers attack and we use the model to estimate the distribution of valid connections. Our model discovers the important factors that determine how harmful the attack is, and it can quantitatively predict the duration of downloading process under the attack. The real-world experimental results match well with our model, which demonstrates that the model is correct and useful.