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Everyday life is more and more dependent on the services provided by highly complex and pervasive critical infrastructures, whose failures might lead to catastrophic consequences in terms of damages to human life, environment, economy.
The thesis presents a work based on the study and research of topics related to resilience and security of complex systems, which present characteristics of heterogeneity, dynamicity, evolvability, interdependencies, interconnections, criticality with respect to the domain of application. Nowadays, the study of such systems and their characteristics is of paramount importance, because they are becoming more and more widespread, affecting our lives and our way of life. For this reason, it is crucial to design such systems with an high level of resilience and security. Indeed, their failures could lead, in the worst case, to catastrophic consequences, for instance if we consider the Critical Infrastructures. Through stochastic model-based approaches, the thesis addresses the system evaluation to support design decision at pre-deployment and run-time, both from resilience and security point of view. The thesis is structured in three main parts.
Initially the focus is on the Electrical Power Systems, specifically on the modelling and assessment of dependability and performance requirements by means of model-based approaches and on the investigation of techniques and mechanisms to apply in order to tolerate unexpected events, failures, or attacks, thus allowing the continuity of the service. The thesis then addresses the study of new modelling approaches for the assessment of systems showing aspects of evolution and dynamicity. Indeed, current systems are more and more conceived as dynamically adaptable and evolvable sets of components, which must be able to modify their behaviour at run-time to tackle the continuous changes happening in the unpredictable open-world settings. In particular the focus is on new approaches useful to combine the benefits of both classic pre-deployment (off-line) analysis, and run-time analysis, by providing solutions that enable a refinement and an improvement of the system model. Finally, the thesis also focuses on aspects of security related to complex systems. Indeed, due to the increasing presence of automatic controlling operation, the massive use of networks to transfer data and information, and the human operations, new security concerns in such systems have been introduced and cannot be neglected. Security issues do not only have direct impact on systems availability, integrity and confidentiality, but they also can influence the dependability, specifically
the safety of critical systems. In this context the thesis mainly focus on security issue related to the insider threats, which are one of the major cause of security
violations.
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