Malicious user behavior that does not trigger access violation or data leak alert is difficult to detect. Using the stolen login credentials, the intruder doing espionage will first try to stay undetected, silently collect data that he is authorized to access from the company network. This paper presents an overview of User Behavior Analytics Platform built to collect logs, extract features and detect anomalous users which may contain potential insider threats. Besides, a multi-algorithms ensemble, combining OCSVM, RNN and Isolation Forest, is introduced. The experiment showed that the system with an ensemble of unsupervised anomaly detection algorithms can detect abnormal user behavior patterns. The experiment results indicate that OCSVM and RNN suffer from anomalies in the training set, and iF orest gives more false positives and false negatives, while the ensemble of three algorithms has great performance and achieves recall 96.55% and accuracy 91.24% on average.