  Surveillance performance is studied for a wireless eavesdropping system,
where a full-duplex legitimate monitor eavesdrops a suspicious link efficiently
with the artificial noise (AN) assistance. Different from the existing work in
the literature, the suspicious receiver in this paper is assumed to be capable
of detecting the presence of AN. Once such receiver detects the AN, the
suspicious user will stop transmission, which is harmful for the surveillance
performance. Hence, to improve the surveillance performance, AN should be
transmitted covertly with a low detection probability by the suspicious
receiver. Under these assumptions, an optimization problem is formulated to
maximize the eavesdropping non-outage probability under a covert constraint.
Based on the detection ability at the suspicious receiver, a novel scheme is
proposed to solve the optimization problem by iterative search. Moreover, we
investigate the impact of both the suspicious link uncertainty and the jamming
link uncertainty on the covert surveillance performance. Simulations are
performed to verify the analyses. We show that the suspicious link uncertainty
benefits the surveillance performance, while the jamming link uncertainty can
degrade the surveillance performance.
