Nowadays, many universities face bandwidth saturation problem caused by several origins. These include youtube abusively use, online games and especially illegal downloading that makes havoc to Peer-toPeer protocol e.g. BitTorrent. The latter is often associated with data piracy and copyright violation. This article aims at presenting on one hand the impact of the use of Peer-to-Peer file sharing traffic on campus bandwidth by observation of BitTorrent traffic and on the other a method for limiting the illicit access to this kind of networks. For this purpose, we used a set of open source tools like wireshak sniffer software to capture Bitorrent traffic. Additionally, using the well-known Snort intrusion detection system with a number of adequate and new rules one can reduce bandwidth saturation problem. This solution allowed in our case, a bandwidth saturation reduction of 35%.