Proactive resilience revisited: The delicate balance between resisting intrusions and remaining available

In a recent paper, we presented proactive resilience as a new approach to proactive recovery, based on architectural hybridization. We showed that, with appropriate assumptions about fault rate, proactive resilience makes it possible to build distributed intrusion-tolerant systems guaranteed not to suffer more than the assumed number of faults during their lifetime. In this paper, we explore the impact of these assumptions in asynchronous systems, and derive conditions that should be met by practical systems in order to guarantee long-lived, i.e., available, intrusion-tolerant operation. Our conclusions are based on analytical and simulation results as implemented in Möbius, and we use the same modeling environment to show that our approach offers higher resilience in comparison with other proactive intrusion-tolerant system models.