Physical Security
Layered defense
Physical security is built in layers that deter, detect, delay, and respond. The outer layer (perimeter, lighting, signage, landscaping) deters; the building envelope (doors, locks, glazing) delays; interior controls (access control, intrusion detection, CCTV) detect and restrict; response (officers, alarms, police) completes the cycle. A control must fit its layer: a camera records events, it does not stop them.
Design principles
CPTED covers natural surveillance, natural access control, territorial reinforcement, and maintenance. Target hardening (bollards, barriers, reinforced doors) addresses vehicle and blast threats and forced entry; standoff distance protects against vehicle-borne explosives. Lighting should support both CCTV images and human observation without glare. Locks are rated by function and grade; electronic access control adds audit trails and quick deactivation but depends on power and network.
Detection and response
Choose sensors by threat: door contacts, passive infrared motion, glass-break, fence sensors. Alarm assessment (video verification) reduces false dispatch. Rule of thumb: delay time must exceed response time. If a barrier delays an intruder two minutes and response takes ten, the barrier is inadequate.
Traps
- Treating CCTV as prevention.
- Buying hardware without a response plan.
- Ignoring how lighting affects camera images.
- Overlooking life-safety egress in lockdown design; doors must still open on egress.
Worked example
A data center entrance: bollards at a safe standoff, a mantrap with two interlocked doors, badge plus PIN, door-held-open alarms, camera coverage on every approach, and guard response within three minutes. Each element covers a different layer; no single item is "the security."