An investigation on the feasibility of the bluetooth frequency hopping mechanism for the use as a covert channel technique.

Adaptive Frequency Hopping is a mechanism included in the Bluetooth standard to minimize the effects of interference from other signals sharing the same frequency band. In this paper, several possible strategies of exploiting the frequency hopping mechanism as a covert channel are discussed. There has been some research presenting ways to make use of covert channels over Bluetooth yet none have explored frequency hopping in this context. Three groups of approaches are presented for sending hidden information by means of exploiting specific properties of the frequency hopping mechanism and the generated hopping sequence. These groups consist of strategies to transmit data hidden in protocol packets, modulated on manipulated hopping sequences or by influencing available channels through jamming, thus limiting possible hop frequencies. These approaches are compared by their bandwidth, ease of implementation as well as the detectability of a communication using these covert channels. We show that there are vast unexplored opportunities for covert communication using the adaptive frequency hopping mechanism used by Bluetooth devices.