2.2 Physical Security

Layered physical defenses

Physical security protects hardware, facilities, and people from unauthorized physical access. Effective plans use defense in depth — multiple overlapping layers like fences, locked doors, badge readers, and security guards — so a single failure doesn't compromise the whole system. This complements digital protections against threats that bypass software entirely.

Authentication in the physical world

Physical access controls mirror digital ones. Something you have (a badge or key fob), something you know (a PIN), and something you are (a fingerprint or retina scan via biometrics) verify identity. Combining factors, like a badge plus PIN, creates stronger, multi-factor physical security.

Detecting and deterring intrusion

Beyond blocking access, systems must detect and log intrusions. Video surveillance, motion sensors, and alarm systems alert staff to unauthorized entry, while security guards and visible cameras act as deterrents. Environmental controls (fire suppression, backup power) also protect equipment from non-human physical threats like fire or power loss.

Key terms

Physical security

Measures that protect hardware, facilities, and people from unauthorized physical access.

Defense in depth

Using multiple overlapping layers of security controls so one failure doesn't compromise the whole system.

Biometrics

Authentication using unique physical traits, like fingerprints or retina scans (something you are).

Multi-factor authentication (physical)

Combining two or more credential types, such as a badge (have) and PIN (know), for stronger security.

Intrusion detection tools

Video surveillance, motion sensors, and alarms used to detect and alert staff to unauthorized access.

Try an AP-style question

Which is a physical security control?

1. Strong password policies
2. Antivirus software on laptops
3. Encrypting a database
4. Badge readers on server room doors