How many down?

The systematic risk of a networked system depends to a large extent on its topology. In this paper, we explore this dependency using a model of risk propagation from the literature on interdependent security games. Our main area of focus is on the number of nodes that go down after an attack takes place. We develop a simulation algorithm to study the effects of such attacks on arbitrary topologies, and apply this simulation to scale-free networks. We investigate by graphical illustration how the outcome distribution of such networks exhibits correlation effects that increase the likelihood of losing more nodes at once -- an effect having direct applications to cyber-insurance.