A Game-Theoretic Approach to Defending Nuclear Instrumentation and Control Systems From Cyber-Threats

Cyber-physical systems consist of interconnected physical processes and computational resources. Because the cyber and physical worlds are integrated, the system’s physical assets are vulnerable to cyber-attack. An attacker who is able to access control inputs and mask measurements can damage the system while remaining undetected. By masking certain measurement signals, an attacker may render part of the state space unobservable, meaning that it is impossible to reconstruct those states. This is called an observability attack. A game-theoretic approach is presented to analyze observability attacks. The attacker’s strategy set includes all possible combinations of masked measurements. The defender’s strategy set includes redundant sensing and direct measurement of state variables. Attacker and defender payoffs are quantified using the responses of the observable and unobservable states. The observability attack game is analyzed for a nuclear balance of plant system. Combinations of sensor omissions are analyzed to find observability attacks with high impact and low detection. The effects of sensor augmentation are examined. A pure strategy Nash equilibrium is identified.