Most critical infrastructures such as the power grid, railway or air traffic control, industrial automation in manufacturing, water/sewage infrastructure, banking system, etc., are cyber physical systems (CPS). Since continued availability of the major functions of these are extremely important for economic and normal lives of people, there is a wide spread concern that these might come under intense cyber attacks. In fact, a number of such cases have occurred in the last decade. Therefore,

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... nding these systems from cyber threats is extremely important. Because of the cyber physical nature of most of these systems, and due to increasing use of networking, embedded computing, and SCADA (Supervisory Control and Data Acquisition) the attack surfaces have grown. In this tutorial, we shall consider some of these cyber threats, discuss the methodologies, tools and techniques for defending such systems, and show how the design of secure cyber physical systems differs from previous design methodologies of CPS systems. In the past, CPS design methodology usually followed a model based engineering approach, where as a first step of the design process --a physics based mathematical model of the physical system, and a control theoretic model of the control system --were integrated in a formal or semi-formal framework. The designers would start from an abstract model, and refine it down to an implementation model in several steps, either formally or informally. The implementation model is then validated for functional correctness, performance, real-time requirements etc. Functional Safety, robustness to input assumptions, reliability under fault assumptions, and resilience to unknown adversities were considered as good design goals.