Today, with the rapid advance in broadband technology, digital contents delivery applications have been used widely and the streaming technology has made the contents delivery more popular. Nowadays, there is high expectation on Digital Rights Management (DRM). Traitor Tracing is one of the DRM technologies and enables us to observe user's contents streaming and detect illegal contents streaming. However, malicious users can interrupt tracing with illegal processes at user-side computers. To prevent all illegal processes at the userside, routers should analyze information embedded into packets, which is unrealistic. In this article, we propose a system to detect illegal contents streaming by using only traffic patterns which are constructed from the amount of traffic traversing routers. We also investigate a method to cope with random errors and burst errors which occur frequently in wireless environment and show the satisfactory result which we have obtained in a practical testing environment.