A real time OCSVM Intrusion Detection module with low overhead for SCADA systems

In this paper we present a intrusion detection module capable of detecting malicious network traffic in a SCADA (Supervisory Control and Data Acquisition) system. Malicious data in a SCADA system disrupt its correct functioning and tamper with its normal operation. OCSVM (One-Class Support Vector Machine) is an intrusion detection mechanism that does not need any labeled data for training or any information about the kind of anomaly is expecting for the detection process. This feature makes it ideal for processing SCADA environment data and automate SCADA performance monitoring. The OCSVM module developed is trained by network traces off line and detect anomalies in the system real time. In order to decrease the overhead induced by communicated alarms we propose a new detection mechanism that is based on the combination of OCSVM with a recursive k-means clustering procedure. The proposed intrusion detection module K−OCSVM is capable to distinguish severe alarms from possible attacks regardless of the values of parameters σ and ν, making it ideal for real-time intrusion detection mechanisms for SCADA systems. The most severe alarms are then communicated with the use of IDMEF files to an IDSIDS (Intrusion Detection System) system that is developed under CockpitCI project. Alarm messages carry information about the source of the incident, the time of the intrusion and a classification of the alarm. Keywords—SCADA systems; OCSVM; intrusion detection