Assessing n-order dependencies between critical infrastructures

The protection of critical infrastructures (CI) is a complex task, since it involves the assessment of both internal and external security risk. In the recent literature, methodologies have been proposed that can be used to identify organisation-wise security threats, or even first-order dependency risk (i.e., risk deriving from direct dependencies). However, there is a lack of work in the area of multi-order dependencies, i.e., assessing the cumulative effects of a single incident, on infrastructures that are connected indirectly. In this paper, we propose a method to identify and assess multi-order dependencies. Based on previous work, we utilise existing first-order dependency graphs, in order to assess the effect of a disruption to consequent infrastructures. In this way, it may be possible to identify and prevent security threats of very high impact from a macroscopic view, which would be hard to identify if we only examine first-order dependencies. We also present a scenario, which provides some evidence on the applicability of the proposed approach.