Optimizing defensive resource allocation in layered systems under the coexistence of strategic and non-strategic risks

Many security systems, such as schools, airports, and public transit, are characterized by multiple layers, where layers are interconnected against various types of attacks. In the literature, there is a lack of studies focusing on how to protect layered systems through optimal resource allocation in the presence of strategic and non-strategic attackers. To address this research gap, this paper makes an initial attempt to study the defensive resource allocation problem in layered systems against the co-existence of strategic and non-strategic risks. Specifically, we develop a novel hybrid resource allocation model, and examine the robustness of the model considering two false beliefs of the defender. We provide numerical illustrations using the real data from U.S. school shootings. Our findings suggest that the defender would benefit from layered structures in a system and achieve lower risks by strengthening the outer layers, as it provides extra levels of defense for the inner layers. The results also show that the pure game theoretic model built solely upon strategic risks may not always the preferred choice for guiding resource allocation, especially when the probability of the attacker being non-strategic is high. This highlights the importance of using the hybrid model to account for the behaviors of attackers.