A Network Intrusion Detection System (NIDS) is a security tool designed to monitor network traffic for suspicious activities and potential threats. It analyzes data packets traveling across the network and identifies patterns that may indicate unauthorized access or attacks. By detecting these anomalies, NIDS helps organizations respond quickly to potential security breaches. NIDS can operate in two main modes: signature-based and anomaly-based. Signature-based systems look for known threats by comparing traffic against a database of attack signatures, while anomaly-based systems establish a baseline of normal behavior and flag deviations from this norm. Together, they enhance network security and protect sensitive information.