What do Network-based Intrusion Detection Systems (NIDS) monitor?

Network-based Intrusion Detection Systems (NIDS) are designed specifically to monitor network traffic in real time. This capability allows NIDS to analyze data packets flowing through the network, identifying patterns or anomalies that may indicate potential security threats or unauthorized activities. By observing the traffic across the entire network, NIDS can recognize malicious behaviors that might not be detected by monitoring individual hosts or systems. This is crucial for identifying widespread attacks that could affect multiple devices.

Monitoring network traffic enables NIDS to function effectively in a dynamic environment where multiple users access various resources simultaneously. It provides a broader view of potential intrusions compared to other systems that focus solely on individual hosts or specific segments of the network. This proactive monitoring helps in early detection and can aid in responding to threats before they escalate into more significant issues.

In contrast, other options refer to narrower scopes of security monitoring, which do not encompass the real-time network-wide oversight that NIDS provides. Hence, option B accurately reflects the primary function of Network-based Intrusion Detection Systems.