This is the accepted version of the paper.This version of the publication may differ from the final published version. Abstract. In this paper we report on a recent study of the impact of cyberattacks on the resilience of complex industrial systems. We describe our approach to building a hybrid model consisting of both the system under study and an Adversary, and we demonstrate its use on a complex case study -a reference power transmission network (NORDIC 32), enhanced with a detailed model of the computer and communication system used for monitoring, protection and control. We studied the resilience of the modelled system under different scenarios: i) a base-line scenario in which the modelled system operates in the presence of accidental failures without cyber-attacks; ii) scenarios in which cyber-attacks can occur. We discuss the usefulness of our findings and outline directions for further work. Permanent repository link

This is the accepted version of the paper.This version of the publication may differ from the final published version. Abstract. The evaluation of the security, reliability and resilience of critical infrastructures (CI) faces a wide range of challenges ranging from the scale and tempo of attacks to the need to address complex and interdependent systems of systems. Model-based approaches and probabilistic design are fundamental to the evaluation of CI and we need to know whether we can trust these models. This paper presents an approach we are developing to justify the models used to assure CI using structured assurance cases based on Claims, Arguments and Evidence (CAE). The modelling and quantitative evaluation of the properties are supported by the Preliminary Interdependency Analysis (PIA) method and platform applied to a case study -a reference power transmission network enhanced with an industrial distributed system of monitoring, protection and control. We discuss the usefulness of the modelling and assurance case structuring approaches, some findings from the case study, and outline the directions of further work. Permanent repository link

Abstract. In this paper we report recent results on modelling the impact of cyber-attacks on the resilience of complex industrial systems. We use a hybrid model of the system under study in which the accidental failures and the malicious behaviour of the Adversary are modelled stochastically, while the consequences of failures and attacks are modelled in detail using deterministic models. This modelling approach is demonstrated on a complex case study -a reference power transmission network (NORDIC 32), enhanced with a detailed model of the computer and communication network used for monitoring, protection and control compliant with the international standard IEC 61850. We studied the resilience of the modelled system under different scenarios: i) a base-line scenario in which the modelled system operates in the presence of accidental failures without cyber-attacks; ii) several different scenarios of cyberattacks. We discuss the usefulness of the modelling approach, of the findings, and outline directions for further work.

This is the accepted version of the paper.This version of the publication may differ from the final published version. Abstract. This paper presents a tool for structuring arguments in assurance cases. The tool is designed to support the methodology of Claims-Arguments-Evidence (CAE) Building Blocks that provides a series of archetypal CAE fragments to help structure cases more formally and systematically. It assists with the development and maintenance of structured assurance cases by providing facilities to manage CAE blocks and partially automate the generation of claim structures. In addition to the tool, new visual guidelines called "Helping hand" is provided to assist in applying the building blocks. The tool has been implemented on the Adelard ASCE platform. The target users are assurance case developers and reviewers. The tool and associated methodology can also be useful for people learning how to structure cases in a more rigorous and systematic manner. Permanent repository linkKeywords: Claims·argument·evidence·CAE building blocks·helping hand·ASCE tool·support. IntroductionOver the past ten years there has been a trend towards an explicit claim-based approach to safety justification and considerable work has been done on developing and structuring assurance cases [1,2,3]. However, the practice of how to structure and present cases is very varied. There are lots of different styles with different expressiveness and these many approaches make it difficult to compare cases and hard to provide a more rigorous semantics. To address these issues and provide a more rigorous approach to architecting cases, we have defined specific rules that restrict the type of argument structures and developed a collection of building blocks for assurance cases that help construct cases more formally and systematically [4]. During the development of CAE building blocks, we reviewed a wide range of cases from the defence, medical, financial and nuclear sector and the proposed set of building blocks were able to capture most of what was being expressed. We wish to deploy these CAE building blocks, evaluating their use and improving the methodology.The tool presented in this paper is designed to aid the research and practice of developing structured formal and semi-formal assurance cases. There are other products [5,6] available to assist in the structured assurance case development. What makes our tool unique is support for the CAE blocks as self-contained reusable configurable components. It is a purpose-built tool designed specifically for the building blocks methodology, therefore, it was essential to integrate it with a widely-used assurance case software to make an impact. We implemented it on top of ASCE [7], which is a marketleading tool for the development and maintenance of assurance cases across a wide range of industries. ASCE is a commercial product but it is available free of charge for academic research purposes.The paper is structured in the following way. The concept of CAE building blocks needed to understan...

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