A dependency graph formalism for the dynamic defense of cyber networks

We present ongoing work related to the development of a security model for the dynamic defense of cyber networks. The model is based on a graphical object termed a dependency graph, which models the interactions between security conditions and exploits. By embedding a state-space on the dependency graph, we are able to reason about the security of the system and prescribe effective defense decision in order to mitigate the progression of an attacker. The resulting defense problem is a partially observable Markov decision process. The application of an existing online solver allows for one to obtain defense policies in realistically-sized systems.