Quantifying Cyber Resilience: A Framework Based on Availability Metrics and AUC-Based Normalization

This study presents a metric selection framework and a normalization method for the quantitative assessment of cyber resilience, with a specific focus on availability as a core dimension. To develop a generalizable evaluation model, service types from 1124 organizations were categorized, and candidate metrics applicable across diverse operational environments were identified. Ten quantitative metrics were derived based on five core selection criteria—objectivity, reproducibility, scalability, practicality, and relevance to resilience—while adhering to the principles of mutual exclusivity and collective exhaustiveness. To validate the framework, two availability-oriented metrics—Transactions per Second (TPS) and Connections per Second (CPS)—were empirically evaluated in a simulated denial-of-service environment using a TCP SYN flood attack scenario. The experiment included three phases: normal operation, attack, and recovery. An Area Under the Curve (AUC)-based Normalized Resilience Index (NRI) was introduced to quantify performance degradation and recovery, using each organization’s Recovery Time Objective (RTO) as a reference baseline. This approach facilitates objective, interpretable comparisons of resilience performance across systems with varying service conditions. The findings demonstrate the practical applicability of the proposed metrics and normalization technique for evaluating cyber resilience and underscore their potential in informing resilience policy development, operational benchmarking, and technical decision-making.