DFS covert channels on multi-core platforms

Covert channels provide a secret communication medium between two malicious processes to exfiltrate information stealthily that violates the security policy of a system. In this paper, we demonstrate a new covert timing channel attack that exploits the CPU operating frequencies with different power governors in real system environment. In particular, we establish how two colluding processes-a trojan and a spy can modulate the CPU frequency to create a powerful, high-capacity and robust covert channel. We implement this covert channel both in a single threaded and simultaneous multi-threading (SMT) environment and show the feasibility of such a communication. Our experiments on Intel Xeon server platform demonstrate dynamic frequency scaling covert channels that can achieve up to 20 bits/second.