CISA Protection of Information Assets Practice Question
An IS auditor is reviewing the physical access controls at a data center. Which of the following is the MOST effective control to prevent tailgating?
⚠ Common exam trap
CISA often tests the difference between preventive and detective physical controls — candidates pick CCTV or guards (detective/deterrent) when the question asks for the MOST effective control to PREVENT tailgating, which requires a physical interlock like a mantrap.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Mantrap
A mantrap is a physical security control consisting of a small vestibule with two interlocking doors, where the first door must close and the person must be authenticated before the second door opens. This design physically prevents tailgating because only one person can occupy the space at a time, and unauthorized individuals cannot slip through behind an authorized person. It is the most effective preventive control specifically engineered to defeat tailgating.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Security guards at the entrance
Why it's wrong here
A guard can challenge unfamiliar faces, yet cannot watch every doorway continuously and may be socially engineered or distracted. Guards suit low-throughput lobbies needing judgement; tailgating prevention requires a physical barrier enforcing one entry per authentication, such as a mantrap or turnstile.
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CCTV cameras at the entrance
Why it's wrong here
CCTV records an incident for later review but does not physically stop a second person slipping through behind an authenticated entrant. Cameras are appropriate for deterrence, monitoring and forensic evidence; preventing tailgating requires a barrier that admits only one person per credential presentation.
- ✓
Mantrap
Why this is correct
A mantrap permits only one person through an interlocking door sequence at a time, physically preventing an unauthorised individual from following an authenticated person. This directly satisfies the stem's constraint by eliminating the single-entry tailgating vector that badge readers alone cannot address.
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Biometric readers at all entrances
Why it's wrong here
Biometric readers authenticate one person per scan but do not detect a second person entering on a single valid authentication, so piggybacking still succeeds. They are the right control where identity assurance per individual matters, such as restricting a high-security room to enrolled staff.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official ISACA exam blueprint
This CISA practice question is part of Courseiva's free ISACA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CISA exam.