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International audience; Web services provide a general basis of convenient access and operation for cloud applications. However, such services become very vulnerable when being attacked, especially in the situation where service continuity is one of the most important requirements. This issue highlights the necessity to apply reliable and formal methods to attack tolerance in Web services. In this paper, we propose a Coloured Petri Nets based method for attack tolerance by modelling and analysing basic behaviours of attack-network interaction, attack detectors and their tolerance solutions. Furthermore, complex attacks can be analysed and tolerance solutions deployed by identifying these basic attack-network interactions and composing their solutions. The validity of our method is demonstrated through a case study on attack tolerance in cloud-based medical information storage.

Diagnosability is a crucial property that determines at design stage how accurate any diagnosis algorithm can be on a partially observable system. Recent work on diagnosability has generalized fault event case to pattern case, which can describe more general objectives for diagnosis problem, but based on global model and global twin plant construction. In this paper, we propose an original framework to solve pattern diagnosability in a distributed way to avoid calculating global objects. We first show how to incrementally accomplish pattern recognition without building global model by propagating only diagnosability relative information between components. Then an efficient way to construct pattern verifier is proposed, which is inspired from the classical twin plant method but with smaller state space, to search for partial critical paths, whose global consistency is subsequently checked. Meanwhile we prove that the result obtained from our distributed approach is on an equality with that from the centralized one but the evaluation result shows that our search state space exploited is only a small subpart of the global twin plant, whose construction is unavoidable in the centralized approach.