A risk-driven security analysis method and modelling language

Abstract

The BT Security Research Centre has defined and continues to develop a modelling language and method for representing and analysing ICT security requirements. The language is used to create a model that serves as a medium for communication between consultant and customer, a guide in making decisions, and the basis of a specification for implementing a solution. Three sub-models deal with business and technical requirements of the ICT system; threats, vulnerability and risks; and security measures and processes. The modelling process is iterative, with decisions being driven by optimisation of business value, trading off risk against cost. This paper focuses on aspects of the method dealing with assessment of risk and analysis of requirements for operational risk management. IntroductionThis paper describes aspects of on-going work within BT's Security Research Centre aimed at producing a modelling language and methodology to support the development and operation of secure systems. This work was introduced in a recent joint paper which described complementary security modelling projects at BT and HP Laboratories [1]. The earlier paper focused on the application of modelling techniques to achieving assurance, i.e. generating confidence (backed with evidence) that a system complies with regulatory and other requirements. It also gave a general motivation for modelling and an overview of both approaches. The current paper updates the overview of the BT method and goes into more detail about the modelling language, stressing aspects relevant to the modelling of risk, and the facilitation of operational risk management. A separate paper does likewise for the HP method [2].The paper begins with a general discussion of modelling in the context of security, before moving on to outline our view of risk -optimisation of security risk is an important driver in the modelling methodology. The three main submodels -the value model, security model and threat model -and the concepts used to construct them, are then introduced. The following sections outline the iterative process by which the models are constructed and refined, focusing on the risk analysis step. We then discuss the relevance of the methodology to operational risk management (ORM) and use of models in ORM tools such as future versions of the BT Risk Cockpit. A survey of related work on security and risk modelling is then provided. The paper concludes with a brief discussion of the current status and activities of the project. Modelling and securityMany engineering and scientific disciplines make use of models. A model is an abstract representation of a system or artefact. Inevitably, a model is an idealisation of, and approximation to, the real system it represents. Abstraction helps modellers focus on particular properties of the system of importance to their purpose. Furthermore, if the model is expressed within a formal framework, then analysis, or manipulation, of the model will make predictions about the real system. Confirmation and refutation of the correct...

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