Entropy-Based Proactive and Reactive Cyber-Physical Security

This chapter considers the problem of securely operating a cyber-physical system under different types of attacks, including actuator and sensor attacks. The proposed defense approach consists of a proactive and a reactive mechanism. The proactive part leverages the principles of moving target defense, and introduces a stochastic switching structure that dynamically and continuously alters the behavior of the system, aiming to neutralize the attacker’s reconnaissance efforts. An unpredictability metric is proposed that utilizes the entropy induced by a switching supervisor, in order to maximize efficiency. The reactive part isolates the potentially compromised system components. A novel integral Bellman-based intrusion detection system is used to detect the attacks and take appropriate measures by collecting data online and without knowledge of the physical interpretation of the system. Simulation results are presented to showcase the efficacy of the proposed approach.