Leak Research Concerning BitTorrent Meta File

BitTorrent is vulnerable to several attacks, since the protocol initially designed lacks of security concerns. Although researches and studies have recently paid lots of attentions on security issues with BitTorrent, a leak in meta file has not been on the agenda yet. In this paper we analyze the design principle of BitTorrent meta file and show the leak which can cause arbitrary data modification of unprotected section, especially the tracker list. We show how attacker injects malicious trackers and peers into BitTorrent by exploiting such leak and some major threats BitTorrent suffers from the injection behavior. In order to fix the leak, we propose an approach which puts the fingerprint of key data in the meta file info dictionary. Experimental results show that the fingerprint can prevent malicious tracker injection from modifying meta file. Results also show the network environment of unmodified file can be protected though attacker may forge fingerprint.