Facade: High-Precision Insider Threat Detection Using Deep Contextual Anomaly Detection

Insiders with privileged access have the power to cause great harm to their organization. Even a single insider threat incident can be catastrophic, resulting in both financial losses and reputation damage. These threats are some of the most difficult to detect, as attack activity is interspersed in large volumes of legitimate activity. Although it is a serious threat, the literature is sparse aside from a few studies with various limitations, preventing their practical deployment in large-scale organizations. We present Facade: fast and accurate contextual anomaly detection, a high-precision, deep-learning system that has served as the last line of defense against insider threats at Google since 2018. Facade is an innovative self-supervised system that detects suspicious events by considering the context surrounding each event, including relevant facts about the user and resource involved. It is built around a new multi-modal model that is trained on corporate document access, SQL table access, and HTTP/RPC request logs. To overcome the scarcity of labeled incident data, Facade employs a novel contrastive learning strategy trained exclusively on benign activity. Facade detects insider attackers with an extremely low false-positive rate, lower than 0.01%. For single rogue events, such as the illegitimate access to a sensitive document, the false-positive rate is as low as 0.0003%. To the best of our knowledge, Facade is the only proposed insider risk anomaly detection system with a false positive rate low enough for use in large corporate environments.