In defense in depth, which component is typically an inner layer?

• A. Perimeter fencing
• B. Access control measures
• C. Lighting at boundary
• D. Surveillance of external grounds

Answer: (B)

In defense in depth, security is built as layers that progress from the outside toward the most protected assets. The inner layer is the controls that actually restrict entry into sensitive areas. Access control measures fit this role best because they require verification of who is allowed to pass and exactly where they’re permitted to go, often using badges, PINs, or biometrics. These controls sit closer to the protected space and can be combined with secure doors, turnstiles, and authorized-access workflows to prevent unauthorized movement even if someone bypasses the outer layers.

Perimeter fencing, lighting at the boundary, and surveillance of external grounds are part of the outer boundary that deters and detects activity from a distance. They help reduce the chance of intrusion but do not themselves decide who gets into the inner areas, which is why they’re not the inner layer.