LIP: A Lifetime and Popularity Based Ranking Approach to Filter out Fake Files in P2P File Sharing Systems

P2P file sharing systems often use incentive policies to encourage sharing. With the decrease of free riders, the amount of cheating behaviors has increased. Some users rename a common file with a popular name to attract the downloads of other users in order to gain unfair advantages from incentive policies. We call the renamed file a fake file. While techniques have been proposed to combat fake files, an effective approach to filter out fake files in existing systems is lacking, especially before a real file comes out. In this paper, we design two detectors to identify fake files by mining historical logs and find that fake files are indeed pervasive. We introduce a metric called lifetime, which is a file’s average retention time in users’ computers, and show that it can be used to distinguish between real and fake files. We then propose a lifetime and popularity based ranking approach to filter out fake files. Experiments are designed with the real and fake files collected by the two detectors, and the results show that this approach can reduce the download volume of fake files both before and after a real file comes out.