Multi-target Risk Score Aggregation for Security Evaluation of Network Environments

Scoring computer systems/networks in terms of specific threats or concerns can enable the comparison of their security level, in a quantitative manner, to facilitate decision making, e.g., mitigation prioritization. The state-of-the-art approaches have mostly focused on scoring the security of a given target, while aggregating scores of multiple systems where each system can be a potential target remains less explored, e.g., whether network A is relatively more secure than network B. In this paper, we take advantage of the well-established attack path representation and use such paths as inter-system influences to derive a risk score of the entire network. We consider the security semantics of various forms of score aggregation, which has not been studied by prior work, and propose to use what we call pairwise path aggregation. We evaluate our approach with a typical fifth Generation (5G) core network, supplemented by evaluations for other network types. The results show that our approach is able to reflect how the overall security varies with multiple factors in common operational scenarios of IT environments.