Which set correctly lists the three lines of defense in crime prevention?

• A. Exterior cameras; interior alarms; security guards.
• B. Only perimeter barrier.
• C. Perimeter barrier; building exterior; interior controls.
• D. Building exterior only.

Answer: (C)

Layered security uses three lines of defense arranged from outside to inside. The outermost line is the perimeter barrier, which establishes the first boundary and slows or blocks unauthorized approach. The next line is the building exterior, including doors, windows, exterior lighting, and exterior-access controls that protect the building envelope. The innermost line is interior controls, such as internal doors, access control inside the building, intrusion alarms, and security procedures that manage movement and detection once someone is inside.

This combination best represents defense-in-depth: if someone bypasses the outer barrier, they still face the exterior building controls, and if they get past those, interior controls help prevent or quickly detect and respond to intrusions. The other options don’t present three distinct, sequential layers of defense, or rely on single elements rather than the full layered approach.