The effect of interdependency on game-theoretic cyber-physical system defense

Cyber-physical systems (CPS) consist of cyber and physical components linked together which are interdependent with each other. These systems are interdependent in complex ways, and failures of a component of the system may have a cascading effect. Ensuring defense on such systems from malicious attack is critical. This research studies the defense strategies on three basic functional interdependent cyber-physical structures based on a simultaneous game model between an attacker and a defender. The player’s utility is evaluated as the difference between her(his) reward and the cost of her(his) action. The pure strategies of Nash equilibrium are obtained for the bus and the star cyber-physical structures, the best responses are obtained for the ring cyberphysical structures. The result shows that both defender’s and attacker’s utilities are high in the star structure with partial interdependency and full failure. The attacker’s utility is higher than the defender’s in star structure with partial interdependency and partial failure. In star structure, the attacker’s and defender’s Nash equilibrium pure strategies are sensitive to different interdependencies whereas in the bus structure, interdependency shows little impact on both defender’s and attacker’s pure NE strategies