Scale-Free Networks and Robustness of Critical Infrastructure Networks

We examine the robustness of critical infrastructure networks, specifically aspects which relate to the network topology. We describe some simulation studies which identify a number of characteristics that make a network robust in the face of terrorist attacks, taking link capacity into account. Our simulations utilise a network analysis package called CAVALIER, which we have developed. Our results confirm the resistance of scale-free networks to random failures, but not to targeted terrorist attacks. We show that physical networks, including telecommunications networks, are not scale-free, and therefore the robustness of other kinds of networks is more relevant to critical infrastructure. However, terrorist organisations are structured as scale-free networks, which suggests that they might themselves be vulnerable. We examine the feasibility of targeting scale-free networks by examining two historical case studies, from the 1 and 14 centuries.