What is anomaly-based detection in an IDS?

Anomaly-based detection refers to the method of identifying unusual patterns or behaviors in a system that deviate from what is considered normal. This approach does not rely on predefined signatures of known threats but instead establishes a baseline of normal operations over time. Once this baseline is established, any significant deviations from it trigger alerts, suggesting a potential security threat or breach, such as unusual traffic levels, unexpected application behavior, or irregular user activity.

The essence of anomaly-based detection lies in its ability to identify new, unknown threats that may not yet have well-documented signatures or definitions. By focusing on abnormal behavior, it can respond to innovative attack vectors that traditional signature-based systems might miss. This makes it particularly valuable in a constantly evolving threat landscape, where attackers often develop new tactics.

While monitoring network traffic for known threats is a proactive security measure, it does not account for the detection of novel attacks. Utilizing firewall rules is more about prevention than detection, and tracking user logins and access patterns provides insights but does not specifically highlight deviations from established norms in the same way anomaly-based detection does. Thus, identifying deviations from normal system behavior is the core function of anomaly-based detection in an Intrusion Detection System (IDS).