Attack and interception in networks

This paper studies a game of attack and interception in a network where a single attacker chooses a target and a path, and each node chooses a level of protection. We show that the Nash equilibrium of the game exists and is unique. We characterize equilibrium attack paths and attack distributions as a function of the underlying network and target values. We show that adding a link or increasing the value of a target may harm the attacker-a comparative statics effect that is reminiscent of Braess's paradox in transportation economics. Finally, we contrast the Nash equilibrium with the equilibrium of a variant of the model: one where all nodes cooperate in interception.