Abstract-Modern society depends on the operations of critical infrastructure system (CIs), such as transportation, energy, telecommunications, and water. Characterized by direct and transitive interdependencies, these systems have become so interconnected that disruption of one may lead to disruptions in all. The levels in critical infrastructures must firstly be classified in order to make a systemic perspective for critical infrastructure system protection). This paper discusses critical infrastructure interdependencies by highlighting some examples of cascading failure phenomena from references and experts. By utilizing the Interpretive Structural Modeling (ISM) methodology, we analyze the interactions of eight critical infrastructures according to their mutual influences, thereby we identify those driving infrastructures, which can aggravate a few more infrastructure and those dependent infrastructures, which are most influenced by driving infrastructure. It can be also observed that there are some infrastructures, which have both high driving power and dependency, thus needing more attention. The approach taken in this research can form the basis for the analysis of the system of systems that represents the CIs
