Early stage denial of service attacks in BitTorrent: an experimental study

BitTorrent is a popular p2p file replication application, which aims at replicating a given content as fast as possible on a set of peers. The algorithms of BitTorrent used to elect remote peers with whom a peer collaborates and also which pieces of the content it offers, have proved to be highly efficient. This means that a high level of parallelism is achieved among the peers as a given peer always has a high chance to find another peer that holds content it is currently missing. Still, at the beginning of a BitTorrent session, pieces of the content have to be obtained from only a few peers (in general a single one called the initial seed) that hold a full copy of the file to be replicated. In this work, we aim at evaluating the ability of a BitTorrent session to survive to a denial of service attack that would disconnect the initial seed from the network. We address this issue through experimentation. Our main conclusion is that BitTorrent is highly resilient to this attack as neither the ability to obtain a full copy of the content nor the actual replication speed are affected by the disconnection of the initial seed if the attack is not carried out at the very early stage of the session.