Network behavior anomaly detection (NBAD) is a security technique used to monitor a network for signs of unusual activity. This technique is designed to dovetail with multiple layers of security to provide complete protection, and it is accomplished with the use of a computer program which monitors the network on a continuous basis. Numerous companies make programs designed for network behavior anomaly detection in various settings.
One advantage to network behavior anomaly detection is that it can be used to address zero day exploits. Zero day exploits occur when a virus is first released or when people first identify a security hole. On the “zero day,” anti-virus and security software programs have not yet identified a profile which could be used to prevent such exploits. Network behavior anomaly detection, however, doesn't have to look for a particular profile, it just looks for unusual activity, which means that it can identify something like a virus before the anti-virus program has been updated.
When a network behavior anomaly detection program identifies something which it thinks is unusual, it will send an alert to an administrator. The administrator can determine what is going on, and decide whether or not to take action. For example, an uptick in outgoing traffic might be the result of the uploading of a large project onto an external server, which means that no action needs to be taken. Conversely, a computer suddenly sending out thousands of emails could be infected with a virus, making action necessary to protect the rest of the network from infection.