Proactive attack: A strategy for legitimate eavesdropping

In this paper, we study a novel approach to eavesdrop the messages of suspicious users for a surveillance purpose. In particular, we consider a scenario in which the legitimate monitor can act as a jamming source and a decode-and-forward relay station that can force the suspicious users to reveal their exchanged messages. Accordingly, the power allocation policies for the jamming signal of the legitimate monitor subject to deterministic and non-deterministic interference channels are considered. On this basis, we derive a closed-form expression for the successful eavesdropping probability to evaluate the system performance. More importantly, our results reveal that the successful eavesdropping probability of the non-deterministic interference channel from the legitimate monitor to the suspicious receiver outperforms the one of the deterministic interference channel.