Covert Channels Based on Jitter Field of the RTCP Header

Covert channels are used to secretly transfer information. Due to the widely existence of network protocols, encoding covert channels into computer network protocols is highly applicable. The jitter field of RTCP header possesses a characteristic that could be used to set up covert channels. Thus, in this paper, a novel covert channel on jitter field is proposed. In order to set up this channel, statistical parameters of the jitter field in the current network are calculated. Then the secret message is modulated into the jitter field according to the parameters obtained. Because of this modulation method, the characteristic of the covert channel is similar to that of the overt channel. We analyzed the natural variation of jitter data and verified the proposed channel. The test result shows that the attacker could not detect the covert channel by its statistical parameters.