Securing Infrastructure Facilities: When does proactive defense help?

TL;DR

This paper uses game theory to analyze when proactive security investments in infrastructure facilities effectively deter attacks, highlighting conditions under which defenders gain advantage and how securing vulnerable facilities impacts overall system security.

Contribution

It provides a complete characterization of equilibrium security strategies in both simultaneous and sequential attacker-defender models, revealing conditions for proactive defense effectiveness.

Findings

Proactive security can fully deter attacks if all vulnerable facilities are secured.

The defender's advantage depends on the relative costs of attack and defense.

Securing vulnerable facilities at appropriate effort levels is crucial for effective deterrence.

Abstract

Infrastructure systems are increasingly facing new security threats due to the vulnerabilities of cyber-physical components that support their operation. In this article, we investigate how the infrastructure operator (defender) should prioritize the investment in securing a set of facilities in order to reduce the impact of a strategic adversary (attacker) who can target a facility to increase the overall usage cost of the system. We adopt a game-theoretic approach to model the defender-attacker interaction and study two models: normal-form game -- where both players move simultaneously; and sequential game -- where attacker moves after observing the defender's strategy. For each model, we provide a complete characterization of how the set of facilities that are secured by the defender in equilibrium vary with the costs of attack and defense. Importantly, our analysis provides a sharp condition relating the cost parameters for which the defender has the first mover advantage. Specifically, we show that to fully deter the attacker from targeting any facility, the defender needs to proactively secure all "vulnerable facilities" at an appropriate level of effort. We illustrate the outcome of the attacker-defender interaction on a simple transportation network. We also suggest a dynamic learning setup to understand how this outcome can affect the ability of imperfectly informed users to make their decisions about using the system in the post-attack stage.