A Risk-Security Tradeoff in Graphical Coordination Games

A system relying on the collective behavior of decision makers can be vulnerable to a variety of attacks. How well can a system operator protect performance in the face of these risks? We frame this question in the context of graphical coordination games, where the agents in a network choose between two conventions and derive benefits from coordinating neighbors, and system performance is measured in terms of the agents' welfare. In this article, we assess an operator's ability to mitigate two types of attacks: 1) broad attacks, where the adversary distributes targeted incentives to all agents in the network; and 2) focused attacks, where the adversary can force a selected subset of the agents to commit to a prescribed convention. The system operator can among a class of distributed algorithms that define the local interactions. Our main contribution characterizes the operator's fundamental tradeoff between security against worst-case broad attacks and vulnerability from focused attacks. We show that this tradeoff significantly improves when the operator selects a decision-making process at random. This article highlights the design challenges a system operator faces in maintaining resilience of networked distributed systems.