Date Added: Dec 2012
Network based attacks have become a serious threat to the critical information infrastructure on which the people depend. Identifying the source of the attackers behind the stepping stone(s), it is necessary to correlate the incoming and outgoing flows or connections of a stepping stone. In this paper, the authors propose a novel watermark-based correlation scheme that is designed specifically to be robust against timing perturbations. Unlike most previous timing based correlation approaches, their watermark-based approach is "Active" in that it embeds a unique watermark into the encrypted flows by slightly adjusting the timing of selected packets. The unique watermark that is embedded in the encrypted flow gives them a number of advantages over passive timing based correlation in resisting timing perturbations by the attacker.