NoDoze: Combatting Threat Alert Fatigue with Automated Provenance Triage

Abstract

—Large enterprises are increasingly relying on threat detection softwares (e.g., Intrusion Detection Systems) to allow them to spot suspicious activities. These softwares generate alerts which must be investigated by cyber analysts to figure out if they are true attacks. Unfortunately, in practice, there are more alerts than cyber analysts can properly investigate. This leads to a “threat alert fatigue” or information overload problem where cyber analysts miss true attack alerts in the noise of false alarms. In this paper, we present N O D OZE to combat this challenge using contextual and historical information of generated threat alert. N O D OZE first generates a causal dependency graph of an alert event. Then, it assigns an anomaly score to each edge in the dependency graph based on the frequency with which related events have happened before in the enterprise. N O D OZE then propagates those scores along the neighboring edges of the graph using a novel network diffusion algorithm and generates an aggregate anomaly score which is used for triaging. We deployed and evaluated N O D OZE at NEC Labs America. Evaluation on our dataset of 364 threat alerts shows that N O D OZE consistently ranked the true alerts higher than the false alerts based on aggregate anomaly scores. Further, through the introduction of a cutoff threshold for anomaly scores, we estimate that our system decreases the volume of false alarms by 84%, saving analysts’ more than 90 hours of investigation time per week. N O D OZE generates alert dependency graphs that are two orders of magnitude smaller than those generated by traditional tools without sacrificing the vital information needed for the investigation. Our system has a low average runtime overhead and can be deployed with any threat detection software.