A stochastic game approach to the security issue of networked control systems under jamming attacks

Abstract

Securing networked control systems (NCSs) from cyber attacks has been a very important issue to keep NCSs reliable and stable. Most existing efforts tackling this issue treat cyber attacks as model-based disturbances to NCSs. But the reality is that intelligent attackers will not follow any prescribed models and in fact they are able to change their attack strategies dynamically and randomly. In this paper, we address this problem and present an optimal defense mechanism for the NCS under jamming attacks based on the stochastic game theory. A two-player zero-sum stochastic game is formulated to model the dynamic interactions between a jammer (attacker) and a sensor transmitter (defender) in the NCS. In this stochastic game, the cost function includes not only the resource costs used to conduct cyber-layer defense and attack actions, but also the possible degraded dynamic performance (indexed by a quadratic state error) of the NCS. With this cost function, the impacts of the interactions between the attacker and the defender on the dynamic performance of the NCS are taken into account when the two players design/change their cyber-layer strategies. The optimal defense mechanism is obtained by solving a stochastic dynamic programming (SDP) problem. Simulation and comparison studies show that the packet-loss rate of the communication channel of the NCS has been greatly reduced and the dynamic performance of the NCS being attacked by an intelligent jammer is much improved when the proposed defense mechanism is deployed.