Delmere Logistics is designing a new distribution centre and wants no single physical failure to expose the goods vault. They plan a perimeter fence, a badge-controlled lobby, an interior locked corridor and a final vault door. Which security principle are they applying by layering these independent controls?
- ADefence in depth, layering several independent controls so no single failure grants entry Correct
- BLeast privilege, granting each worker only the access their job requires
- CSeparation of duties, splitting a sensitive task across two different people
- DFail-safe defaults, ensuring a door reverts to a locked state on power loss
Why A is correct: Defence in depth stacks independent controls so an attacker must defeat each in turn, which is exactly what the fence, lobby, corridor and vault door achieve.
Why B is wrong: Least privilege limits what an individual may access, but it does not describe stacking multiple independent physical barriers around one asset.
Why C is wrong: Separation of duties is tempting because both aim to reduce risk, but it divides responsibility for a task rather than layering barriers around a facility.
Why D is wrong: Fail-safe defaults concern the state a single control adopts on failure, not the strategy of arranging many controls in successive layers.