A Network-based Intrusion Detection System (NIDS) monitors all network traffic for signs of suspicious activity across multiple hosts. In large environments with critical assets (e.g., financial or healthcare networks), NIDS is ideal because it provides visibility into entire network segments, not just individual systems.

NIDS can be deployed at strategic points (e.g., DMZs, VLANs, subnets) to detect unauthorized access, malware activity, or policy violations.

Reference – CEH v13 Official Courseware:

Module 13: Evading IDS, Firewalls, and Honeypots

Quote:

“Network-based IDS monitors traffic across an entire subnet or segment and is most effective in large environments to detect malicious activity before it reaches critical assets.”

Incorrect Options Explained:

A. Honeypots attract and log attacker behavior, but do not provide network-wide detection.

B. Firewalls filter traffic but are not detection systems.

D. HIDS monitors activity on a single host only.

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