Layered Physical Controls

You’ll be able to

Explain defense in depth for facilities and equipment
Apply the idea to evidence from a realistic technology scenario
Justify a decision using security, reliability, cost, and user impact

Layered Physical Controls

Defense in depth combines deterrent, preventive, detective, and corrective controls. A locked door may prevent entry, a camera records evidence, an inventory detects loss, and a recovery plan restores operations. Layers matter because every single control can fail.

Decision lens

Strong technical decisions connect evidence → mechanism → impact → response. Identify what the evidence shows, explain the system behavior that produced it, state the likely effect on people or data, and choose a response that addresses the cause without creating unnecessary disruption.

Worked example

A server room uses badge access, but the door can be held open and no one reviews entry records.

1.Badge access is preventive but tailgating defeats it.
2.A door alarm or staffed checkpoint can detect propping and unauthorized entry.
3.Regular log review turns collected data into a detective control.
4.Visitor escort and least-privilege badge access reduce exposure.

Answer: Add anti-tailgating and monitoring layers, then assign responsibility for reviewing alerts and logs.

Checkpoint

Why is an unread access log a weak control?

Checkpoint

Which response best demonstrates complete reasoning about defense in depth for facilities and equipment?

On the exam

For a scenario about defense in depth for facilities and equipment, identify the decisive evidence before naming a response. A defensible conclusion here is: Add anti-tailgating and monitoring layers, then assign responsibility for reviewing alerts and logs.

Answer the 2 checkpoints as you read.