What is a network access control (NAC) and how does it help detect rogue devices?

• A. NAC only monitors network traffic; it does not enforce policy.
• B. Network access control enforces policy to allow only compliant devices.
• C. NAC replaces antivirus software.
• D. NAC is a hardware firewall.

Answer: (B)

NAC enforces access policy at the point a device tries to join the network. It authenticates the device and checks its security posture before granting access. Posture checks might include whether the endpoint is managed, has up-to-date patches, an active antivirus, a enabled firewall, and other security requirements defined by the organization. If a device meets the policy, it receives access appropriate to its role; if not, it’s blocked or placed in a restricted/quarantine network to prevent broader access.

This enforcement is how rogue devices are detected: an unauthorized or noncompliant device cannot pass the posture checks, so it is denied access or isolated and logged for remediation. NAC is about actively enforcing policy, not just monitoring, and it’s distinct from antivirus on the endpoint or from a traditional hardware firewall.