Secrecy in defensive allocations as a strategy for achieving more cost-effective attacker deterrence

We discuss strategic interactions between an attacker and either centralized or decentralized defenders, and identify conditions under which centralized defender decision making is preferred. One important implication of our results is that partial secrecy about defensive allocations (disclosure of the total level of defensive investment, but secrecy about which resources are defended) can be a strategy for achieving more cost-effective attack deterrence. In particular, we show that such partial secrecy can be potentially beneficial when security investments are discrete (e.g., as in the use of air marshals to counter threats to commercial aviation).