diMiTrios serpanos, a nd howard shrobe cyber means alone was first demonstrated in the well-known Aurora experiment where a pure cyber attack successfully destroyed a diesel generator [2]; Stuxnet [3] and the recent Ukrainian smartgrid attack [4] as well as several additional less known incidents have demonstrated the potential of cyber attacks to inflict serious societal damage. Finally, ICSs may be compromised to serve as elements of a Botnet as the recent Mirai attack indicates [5]. To address reliability and security in ICSs, one needs to take into account the characteristics of OT technology that differentiates ICSs from typical IT systems, because this influences the security methods and solutions that are appropriate for ICSs. ICSs typically have real-time requirements, often hard ones, whose violation may have significant, or even catastrophic, results. It is important to note that func