Physical Security
Layered physical defense
Physical security protects people, property, and information. Think in concentric layers: site perimeter, building envelope, interior zones, and asset-level protection. Each layer should delay intrusion long enough for detection and response. Understand CPTED (crime prevention through environmental design) principles - natural surveillance, access control, and territorial reinforcement - because questions often ask how to reduce risk through design rather than hardware.
Controls and technologies
Know access control fundamentals: credential types (something you know, have, are), reader technologies, mantrap and turnstile design, and the importance of anti-passback and tailgating prevention. Understand intrusion detection sensors (perimeter, motion, glass-break), alarm monitoring and response, and CCTV's role as a detective and deterrent control with limitations (coverage, retention, privacy). Fire suppression, lighting, bollards, and visitor management are all fair game.
Traps to expect
- Choosing CCTV as a preventive answer when the scenario demands stopping entry; CCTV is primarily detective.
- Ignoring life-safety codes: egress must never be blocked by security hardware, and fail-safe versus fail-secure locking matters.
- Overlooking insider and tailgating risk when a question emphasizes badge readers.
- Assuming more cameras equal better security without coverage analysis or monitoring.
Rule of thumb
Security and life safety conflict? Life safety wins. For any physical control, ask: does it delay, detect, or respond - and is there a person or process to act on the alarm?
Worked example: A data center wants to stop piggyback entry at the main door. The best answer is a mantrap with anti-passback and one-person-per-badge enforcement, not additional cameras, because the loss requires prevention at the entry point.