In this paper, a novel covert channel, called covert behavior channel, is proposed according to behaviors of network users to solve the security and efficiency problem of the traditional covert channel. In the proposed channel, operation sequences of the network protocols are used as carriers of covert information. An encryption-based information embedding scheme is designed to improve security of the covert information. With the help of Markov model, the capacity of the proposed covert channel with time-varying noise is derived. The formulation for analyzing the covert behavior channel is presented against the channel noise aroused by discarding packets. By introducing corrected entropy-based algorithm to detect the covert behavior channel, the security of the channel is verified. Numerical results show that the proposed covert behavior channel is more secure than covert storage channels and achieves a better bit rate and robustness than that of covert timing channels. Copyright (c) 2016 John Wiley & Sons, Ltd.