Sim-Watchdog: Leveraging Temporal Similarity for Anomaly Detection in Dynamic Graphs

Graphs are widely used to characterize relationships or information flows among entities in large networks or distributed systems. In this work, we propose a systematic framework that leverages temporal similarity inherent in dynamic graphs for anomaly detection. This framework relies on the Neyman-Pearson criterion to choose similarity measures with high discriminative power for online anomaly detection in dynamic graphs. We formulate the problem rigorously, and after establishing its inapproximibility result, we develop a greedy algorithm for similarity measure selection. We apply this framework to dynamic graphs generated from email communications among thousands of employees in a large research institution and demonstrate that it works effectively on a set of more than 100 candidate graph similarity measures.