“System-of-systems” approach for interdependent critical infrastructures

The study of the interdependencies within critical infrastructures (CI) is a growing field of research as the importance of potential failure propagation among infrastructures may lead to cascades affecting all supply networks. New powerful methods are required to model and describe such “systems-of-systems” (SoS) as a whole. An overall model is required to provide security and reliability assessment taking into account various kinds of threats and failures. A significant challenge associated with this model may be to create “what-if” scenarios for the analysis of interdependencies. In this paper the interdependencies between industrial control systems (ICS), in particular SCADA (Supervisory Control and Data Acquisition), and the underlying critical infrastructures to address the vulnerabilities related to the coupling of these systems are analyzed. The modeling alternatives for system-of-systems, integrated versus coupled models, are discussed. An integrated model contains detailed low level models of (sub)systems as well as a high level model, covering all hierarchical levels. On the other hand, a coupled model aggregates different simulated outputs of the low level models as inputs at a higher level. Strengths and weaknesses of both approaches are analyzed and a model architecture for SCADA and the “system under control” are proposed. Furthermore, the HLA simulation standard is introduced and discussed in this paper as a promising approach to represent interdependencies between infrastructures. To demonstrate the capabilities of the HLA standard for the interdependencies study, an exemplary application and some first results are also briefly presented in this paper.