Which option does NOT align with the defense-in-depth approach?

Which option does NOT align with the defense-in-depth approach?

• A. Physical security measures
• B. Access controls
• C. Regular patch management
• D. A single firewall at the perimeter

Answer: (D)

Defense-in-depth means stacking protective layers across people, processes, and technology so if one barrier fails, others still stand between assets and harm. Physical security measures, access controls, and regular patch management each add a distinct layer: physical security stops tampering and theft of equipment; access controls limit who can do what even inside the system; patch management reduces the chances that known vulnerabilities can be exploited. Having a single firewall at the perimeter only provides one line of defense. If that boundary is breached, there’s no additional internal segmentation, monitoring, or control to slow or stop an attacker. It creates a single point of failure and misses the multiple, overlapping protections that defense-in-depth relies on.

Defense-in-depth means stacking protective layers across people, processes, and technology so if one barrier fails, others still stand between assets and harm. Physical security measures, access controls, and regular patch management each add a distinct layer: physical security stops tampering and theft of equipment; access controls limit who can do what even inside the system; patch management reduces the chances that known vulnerabilities can be exploited.

Having a single firewall at the perimeter only provides one line of defense. If that boundary is breached, there’s no additional internal segmentation, monitoring, or control to slow or stop an attacker. It creates a single point of failure and misses the multiple, overlapping protections that defense-in-depth relies on.