Stochastic Modeling of Intrusion Tolerant Systems Based on Redundancy and Diversity

To cope with unforeseen attacks to software systems in critical application domains, redundancy-based ITSs schemes are among popular countermeasures to deploy. Designing the adequate ITS for the stated security requirements calls for stochastic analysis supports, able to assess the impact of variety of attack patterns on different ITS configurations. As contribution to this purpose, a stochastic model for ITS is proposed, whose novel aspects are the ability to account for both camouflaging components and for correlation aspects between the security failures affecting the diverse implementations of the software cyber protections adopted in the ITS. Extensive analyses are conducted to show the applicability of the model; the obtained results allow to understand the limits and strengths of selected ITS configurations when subject to attacks occurring in unfavorable conditions for the defender.