Which technology prevents unauthorized users or devices from accessing a private network?

Which technology prevents unauthorized users or devices from accessing a private network?

• A. Network Access Control (NAC)
• B. Virtual Private Network (VPN)
• C. Secure Shell (SSH)
• D. Wireless IDS (WIDS)

Answer: (A)

Network Access Control focuses on who or what can actually join the network by enforcing security policies at the point of connection. It checks both identity (are you authorized) and device health (is the device compliant with security requirements) before granting access, often using 802.1X authentication and posture assessments. If a device passes, NAC places it on the appropriate network segment; if it doesn’t, it can be quarantined or blocked. This proactive enforcement is what prevents unauthorized users or devices from accessing the private network in the first place.

VPN provides an encrypted tunnel for remote connections but does not by itself deny access to the private network for devices that haven’t passed a policy check. SSH is a secure remote management protocol, not a mechanism for controlling general network access. Wireless IDS monitors for suspicious wireless activity and alerts on intrusions, rather than enforcing access control at the point of connection.

So the best fit is Network Access Control.