A Sequential Game of Defense and Attack on an Interdependent System of Systems

This research studies defense strategies of an interdependent system in the face of rational attacks. We propose a sequential game between an attacker and a defender for an interdependent System of Systems (SoS) to explore the effect of interdependency on an optimal defense strategy. We develop an algorithm of backward induction to obtain the Nash equilibrium of the game. The attacker is the first mover as he applies an attack strategy on constituent systems that maximizes his utility. The defender observes and responds by a defense strategy that maximizes her utility. Both players' utilities are expressed as the difference between a player's reward due to SoS functionality (dysfunctionality) and the cost of the action. The sensitivity analysis compares the effects of different parameters on the attacker's and defender's strategies such as the effectiveness of defense (attack), the unit cost of defense (attack) and the interdependency level of constituent systems.