Hiding Skype VoIP Calls from Parametric Identification

The proliferation of wideband connections and the use of more innovative technological platforms in both the business and the private market have caused a shift of the phone traffic from traditional circuit switched networks to packet switched IP based networks in the so-called Voice Over IP revolution. The flexibility of VoIP in general and of Voice Over Internet in particular comes at a price: the lack of a dedicated carrier infrastructure makes extremely hard to identify calls and to track them, thus lawful interception has turned extremely difficult as voice is mixed and randomly interleaved with generic data traffic. In past works it has been demonstrated the feasibility of call identification based on statistical parameters of data flow. However, we argue that it is extremely easy to “poison” the statistical characteristics of a VoIP stream making it stealthy without compromising its acoustical quality and we prove it first implementing a statistical detector showing a larger than 95% accuracy in detection and then a simple program capable of scrambling the statistical characteristics of Skype data streams.