Entropy based taxonomy of network convert channels

In this paper, we examine general mechanisms that a network covert channel may exploit, and we characterize the essence of network covert channels, which are decided by overt sources. So we present a taxonomy of network covert channels based on entropy of overt sources. We classify overt sources into three categories, as variety entropy, constrant entropy and fixed entropy sources, and name the network covert channels correspondingly. For each category we give the definition, meaning, and countermeasure method. Then we group classical network covert channels emerged in 30 years and representational network covert channels proposed in recent 3 years into our taxonomy framework.