Cyber Physical system(CPS) has become the buzz word in recent days for research community in academics and in industries.The great deal of attention drawn by CPS is due its potential to provide far-reaching solutions and applications for all areas of our everyday life. Information and communication technologies (ICT) are strong driving forces of innovation.These two forces for innovation merge to form a CPS.Cyberphysical systems (CPSs) are next generation of engineered systems in which computing, communication, and control technologies are tightly integrated to achieve stability, performance, reliability, robustness, and efficiency in dealing with physical systems of many application domains,[2].One of the application domain of CPS is Medical Cyber-Physical Systems (MCPS), which are life-critical, context-aware, networked systems of medical devices[3].Cyber-physical systems will play a decisive role as a fundamental component of intelligent power networks, or so-called smart grids where network management, consumption optimization and production planning can only be implemented through networked systems. Modeling of such Future CyberPhysical Energy Systems for Distributed Sensing and Control is studied in[4].Agriculture is another field for the use of cyber-physical systems.automobile industry has shown the potential and versatility of CPS more boldly than any other industry. Innovation in this area will increase passenger safety and comfort.Many attempts are made in that direction for modeling of Automotive System ([REF 5]).

CPS includes the physical system which directly interacts with the physical world around and can have major impact on human and environmental safety.Misbehavior caused by whatsoever reason can lead to damage of physical infrastructure being controlled and can lead to chaos. Many instances of security breach had been recorded in past for supervisory control and data acquisition as described in [6].Attacks were also made on natural gas pipeline systems [7], trams [8], power utilities [9], and water systems [10].CPS suffers from specific vulnerabilities which needs special concerns from researchers.the approach followed is to study the effect of specific attack on a particular system. for example,[11] studiesdeceptionanddenial of serviceattacks against a networked control system to find an (optimal) causal feedback controller that minimizes a given objective function subject to safety and power constraints.In [12] authors identified a previously unknown vulnerability in the current techniques aimed at detecting and identifying bad measurements for state estimation in electric power grids.The implications of this vulnerability were investigated through presenting and analyzing a new class of attacks, called false data injection attacks, against state estimation in electric power systems. Effect of replay attack on given control system is analyzed in [12].This paper contributes in 1) providing conditions on the feasibility of the replay attack on the aforementioned system and 2) proposing a countermeasure that guarantees a desired probability of detection (with a fixed false alarm rate) by trading off either detection delay or LQG performance, either by decreasing control accuracy or increasing control effort.In [13] authors summarizes and extends results on the security of cyber-physical systems based on geometric control theory.A typical model for Cyber physical system is shown in Fig 1. components of CPS includes1. Physical Plant : This corresponds to P aspects of CPS.Physical dynamics of any plant or process are captured here.These dynamics changes with respect to time and are governed by physical process itself.Example includes frequency fluctuations in power grid, or positions and velocities of robots, or vehicle densities along a high way.2. Computational Component: it consists of sensors, actuators, one or more computers, and (possibly) one or more operating systems.Sensors are used to sense physical dynamics.there could be multiple sensors and actuators.Actuators take the action as per the control law designed.the action taken is dependent on the sensed physical quantity from physical process.3. Communication Network:It is fundamental characteristic of CPS which is meditating between the computation and physical components,if they are not co located.It can be wired or wireless communication media.

REF: [11CyberPhysical Systems: A Perspective at the Centennial [2] R.Rajkumar,I.Lee,L.Sha,andJ.Stankovic, B Cyber-physical systems: The next computing revolution,[ in Proc. 47th Design Autom. Conf., 2010, pp. 731736.[3] I. Lee and O. Sokolsky, Medical cyber physical systems, inProc. 47th ACM/IEEE Des. Autom. Conf., Jul. 2010, pp. 743748.

[4] M. D. Ilic L. Xie, U. A. Khan, and J. M. F. Moura, Modeling of future cyber-physical energy systems for distributed sensing and control,IEEE Trans. Syst., Man, Cybern. A, Syst., Humans, vol. 40, no. 4, pp. 825838, Jul. 2010.[5] FOR AUTOMOTIVE .\

[6] J. Slay and M. Miller, BLessons learned from the Maroochy water breach,[ in Critical Infrastructure Protection, vol. 253, E. Goetz and S. Shenoi, Eds. Boston, MA: Springer-Verlag, 2007, pp. 7382.[7] S. E. Schechter, J. Jung, and A. W. Berger, BFast detection of scanning worm infections,[ in Proc. 7th Int. Symp. Recent Adv. Intrusion Detection, 2004, pp. 5981.[8] J. Leyden, BPolish teen derails tram after hacking train network,[ The Register, 2008. [Online]. Available:http://www.theregister.co.uk/2008/01/11/tram_hack/.[9] A. Greenberg, BHackers cut cities power,[ Forbes, 2008. [Online]. Available:http://www.forbes.com/2008/01/18/cyber-attack-utilities-tech-intel-cx_ ag_0118attack.html.[10] R. Esposito, BHackers penetrate water system computers,[ ABC News, 2006. [Online]. Available:http://abcnews.go.com/blogs/headlines/2006/10/hackers_penetra/.[11]S. Amin, A. Ca rdenas, and S. Sastry, Safe and secure networked control systems under denial-of-service attacks, inHybrid Systems: Computation and Control, vol. 5469, Apr. 2009, pp. 3145.[12] Y. Mo and B. Sinopoli, Secure control against replay attacks, inAllerton Conf. on Communications, Control and Computing, Monti- cello, IL, USA, Sep. 2010, pp. 911918.