Detecting Bitrate Modulation-Based Covert Voice-Over-IP Communication

Steganography based on bitrate modulation is a new type of information hiding approach for Voice over IP (VoIP), which can naturally resist state-of-the-art steganalysis schemes, due to inducing no modifications on the involved protocols and payloads of VoIP packets. To fill this gap, this letter presents a new corresponding detection scheme. Specifically, for the existing three methods based on bitrate modulation, we first reveal obvious regularities for the change intervals of bitrates in steganographic frame streams, which are totally different from the normal streams. Furthermore, exploiting the statistical properties of change intervals, we design a support-vector-machine-based steganalysis scheme. We evaluate the detection performance of the proposed scheme, respectively, with three state-of-the-art rate adaptation algorithms as the generators of normal VoIP streams. The results demonstrate that the proposed scheme can effectively detect the existing three bitrate modulation-based steganographic methods, even at relatively low covert bandwidths.