1. Overview Anomaly detection is a technique used for identifying rare items, events or observations, which deviate significantly from the majority of the data and do not conform to a well defined notion of normal behavior wikipedia. Anomaly detection has very wide applications, such as Fraud detection in credit card transactions ref, Network Intrusion detection ref, and Cancer cell detection ref. A wide spectrum of techniques have been proposed for anomaly detection, some of the popular methods are: Density-based techniques (e.