Cyber Resilience-by-Construction: Modeling, Measuring & Verifying

The need of cyber security is increasing as cyber attacks are escalating day by day. Cyber attacks are now so many and sophisticated that many will unavoidably get through. Therefore, there is an immense need to employ resilient architectures to defend known or unknown threats. Engineer- ing resilient system/infrastructure is a challenging task, that implies how to measure the resilience and how to obtain sufficient resilience necessary to maintain its service delivery under diverse situations. This paper has two fold objective, the first is to propose a formal approach to measure cyber resilience from different aspects (i.e., attacks, failures) and at different levels (i.e., pro-active, resistive and reactive). To achieve the first objective, we propose a formal frame- work named as: Cyber Resilience Engineering Framework (CREF). The second objective is to build a resilient system by construction. The idea is to build a formal model of a cyber system, which is initially not resilient with respect to attacks. Then by systematic refinements of the formal model and by its model checking, we attain resiliency. We exemplify our technique through the case study of simple cyber security device (i.e., network firewall).