Network-Based Intrusion Detection Systems (NIDS) are security tools designed to monitor network traffic for suspicious activities and potential threats. They analyze data packets traveling across a network to identify patterns that may indicate unauthorized access or attacks. By examining this traffic in real-time, NIDS can alert administrators to potential security breaches. These systems typically use various detection methods, including signature-based detection, which looks for known threats, and anomaly-based detection, which identifies unusual behavior. NIDS can be deployed at strategic points within a network to provide comprehensive coverage and enhance overall security posture against cyber threats.