An Approach to the Consideration of Uncertainties in Cost-Benefit Optimal Design of Physical Security Systems

Abstract

The importance of (physical) security is increasingly acknowledged by society and the scientific community. In light of increasing terrorist threat levels, numerous security assessments of critical infrastructures are conducted and researchers continuously propose new approaches. Moreover, consideration is given to how security measures need to be (re)designed to address the findings of the assessments, taking into account the potentially costly nature of security investments. At the same time, however, assessments suffer from the fundamental problem of inherent uncertainties regarding threats and capabilities of security measures due to little evidence of actual attacks. In this paper, we combine previous work on the concept of security margins with an approach for cost-benefit optimal allocation of available resources considering budgetary constraints to form a three-step approach. In a first step, a security system is assessed for potential vulnerabilities. If such are found, most relevant model parameters are identified on barrier level via sensitivity analysis in a second step. In a third step, security margins are determined for these parameters by optimization, taking into account uncertainties in the assessment as well as cost constraints due to total available budget. The approach is demonstrated using a notional airport structure as an example. The optimization is performed for various budgets to investigate the influence of the budget on system vulnerability and allocation of resources to security measures.