Security Audits Revisited

Rainer Böhme

Abstract: Security audits with subsequent certification appear to be the tool of choice to cure failures in providing the right level of security between different interacting parties, e.,g., between an outsourcing provider and its clients. Our game-theoretic analysis scrutinizes this view and identifies conditions under which security audits are most effective, and when they are not. We find that basic audits are hardly ever useful, and in general, the thoroughness of security audits needs to be carefully tailored to the situation. Technical, managerial, and policy implications for voluntary, mandatory, unilateral, and bilateral security audits are discussed. The analysis is based on a model of interdependent security which takes as parameters the efficiency of security investment in reducing individual risk, the degree of interdependence as a measure of interconnectedness, and the thoroughness of the security audit.