Evaluating the network diversity of networks against zero-day attacks

Diversity has long been regarded as a security mechanism and it has found new applications in security, e.g., in cloud, Moving Target Defense (MTD), and network routing. However, most existing efforts rely on intuitive and imprecise notions of diversity, and the few existing models of diversity are mostly designed for a single system running diverse software replicas or variants. At a higher abstraction level, as a global property of the entire network, diversity and its effect on security have received limited attention. In this chapter, we present a formal model of network diversity as a security metric. Specifically, we first devise a biodiversityinspired metric based on the effective number of distinct resources.We then propose two complementary diversity metrics, based on the least and the average attacking efforts, respectively. Finally, we evaluate the proposed metrics through simulation.