How does a Network IDS (NIDS) primarily monitor communications?

A Network Intrusion Detection System (NIDS) primarily monitors communications by placing itself at key points on the network, often referred to as privileged points, such as a mirrored port. This allows the NIDS to effectively observe and analyze the traffic passing through, enabling it to detect suspicious activities, intrusions, or potential security threats in real time. By being positioned to intercept incoming and outgoing data packets, the system can perform thorough inspections and generate alerts based on predefined security policies or behaviors indicative of malicious activity.

The other options focus on methods or technologies that do not align with the specific function and placement of a NIDS. Monitoring user behavior on endpoints is more characteristic of endpoint detection systems, firewall configurations primarily involve controlling traffic rather than monitoring it for intrusion detection, and standalone software on individual devices would pertain to host-based intrusion detection systems rather than network-based monitoring like a NIDS.