The positive force of deterrence: Estimating the quantitative effects of target shifting

The installation of a protection system can provide protection by either deterring or stopping an attacker. Both modes of effectiveness-deterring and stopping-are uncertain. Some have guessed that deterrence plays a much bigger role than stopping force. The force of deterrence should therefore be of considerable interest, especially if its effect could be estimated and incorporated into a larger risk analysis and business case for developing and buying new systems, but nowhere has it been estimated quantitatively. The effect of one type of deterrence, namely, influencing an attacker's choice of targets-or target shifting, biasing an attacker away from some targets toward others-is assessed quantitatively here using a game-theoretic approach. It is shown that its positive effects are significant. It features as a force multiplier on the order of magnitude or more, even for low-performance security countermeasures whose effectiveness may be compromised somewhat, of necessity, in order to keep the number of false alarms serviceably low. The analysis furthermore implies that there are certain minimum levels of stopping performance that a protection should provide in order to avoid attracting the choice of attackers (under deterrence). Nothing in the analysis argues for complacency in security. Developers must still design the best affordable systems. The analysis enters into the middle ground of security, between no protection and impossibly perfect protection. It counters the criticisms that some raise about lower-level, affordable, sustainable measures that security providers naturally gravitate toward. Although these measures might in some places be defeated in ways that a non-expert can imagine, the measures are not for that reason irresponsible or to be dismissed. Their effectiveness can be much greater than they first appear.