ABSTRACT
In recent years, security of NCSs has received considerable attention since the networks of NCSs render the control system a potential target to a variety of attacks [32]. Since control systems can be regarded as the connection of the information world and physical world, any successful attacks on NCSs might lead to significant loss of property or even human lives. Owing to the rapid development of sensing techniques, sampling intervals of modern industrial control systems are normally quite small, and a sampled-data problem becomes very critical in system design. The delta operator approach has been well recognized in addressing sampling issues for NCSs [160]. Numerical-stiffness problems resulting from the fast sampling protocol can be circumvented by using the delta operator approach [162]. Actually, it has already been reported in [81] and [103] that systems in a number of critical infrastructures were compromised by a series of attacks. Up to now, cyber attacks compromise NCSs mainly by corrupting the integrity or availability of the measurement and actuator data. It is noted that the physical attack is also addressed, which is often launched along with the cyber attacks. Therefore, a natural idea is to develop a more comprehensive attack model for NCSs that simultaneously includes integrity attacks, availability attacks, and physical attacks. On the other hand, how to assess the security level before adversarial incidents occur is also significant, because one can verify whether the system remains within the safety region with the applied security or control strategies.
