Quick Answer
The answer is a mantrap with biometric and badge authentication. This physical security control is most effective because it enforces strict two-person authentication, requiring both the contractor and the employee to independently verify their identities before the mantrap doors unlock, thereby eliminating the social engineering vector of tailgating. On the Certified Ethical Hacker CEH exam, this scenario tests your understanding of layered physical security and the specific weakness of single-factor biometric systems when combined with human courtesy. A common trap is choosing a simple turnstile or security guard, but these fail to prevent piggybacking when an employee holds the door. Remember the memory tip: “Mantrap means one trap per person”—each authentication cycle allows only one individual to pass, directly blocking unauthorized entry.
This CEH practice question tests your understanding of social engineering and physical security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are a security consultant for a mid-sized company with 500 employees. The company has a secure data center with a biometric access control system. Recently, a contractor was able to enter the data center without authorization by claiming he forgot his badge and an employee held the door for him. The contractor then accessed sensitive servers and exfiltrated data. The company wants to prevent such incidents. Which physical security control would be most effective in preventing this type of attack?
Install CCTV cameras to monitor the entrance.
Why wrong: CCTV is detective, not preventive.
Require employees to wear RFID badges at all times.
Why wrong: Badges do not prevent tailgating.
Implement a mantrap with biometric and badge authentication.
Mantraps physically prevent tailgating by requiring one person at a time.
Hire additional security guards at the entrance.
Why wrong: Guards can be socially engineered.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Implement a mantrap with biometric and badge authentication.
Option C is correct because a mantrap with biometric and badge authentication enforces strict two-person authentication: both the contractor and the employee must independently authenticate before the mantrap doors unlock. This prevents tailgating (piggybacking) by ensuring only one person enters per authentication cycle, eliminating the social engineering vector where an employee holds the door for an unauthorized individual.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Install CCTV cameras to monitor the entrance.
Why it's wrong here
CCTV is detective, not preventive.
Require employees to wear RFID badges at all times.
Why it's wrong here
Badges do not prevent tailgating.
Implement a mantrap with biometric and badge authentication.
Why this is correct
Mantraps physically prevent tailgating by requiring one person at a time.
Related concept
Read the scenario before looking for a memorised answer.
Hire additional security guards at the entrance.
Why it's wrong here
Guards can be socially engineered.
Common exam traps
The trap here is that candidates often choose CCTV or guards because they seem like obvious physical security measures, but the question specifically targets tailgating/piggybacking, which only a mantrap with dual authentication can reliably prevent.
Detailed technical explanation
A mantrap typically uses two interlocking doors with a small vestibule; the first door must close and lock before the second door can be opened, and both biometric and badge authentication are required for each individual. This enforces a 'one person, one authentication' rule, which is the only reliable defense against tailgating. In real-world scenarios, even high-security facilities like data centers and server rooms deploy mantrap systems to meet compliance standards such as ISO 27001 or PCI DSS, which mandate physical access controls that prevent piggybacking.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Social Engineering and Physical Security — This question tests Social Engineering and Physical Security — Read the scenario before looking for a memorised answer..
The correct answer is: Implement a mantrap with biometric and badge authentication. — Option C is correct because a mantrap with biometric and badge authentication enforces strict two-person authentication: both the contractor and the employee must independently authenticate before the mantrap doors unlock. This prevents tailgating (piggybacking) by ensuring only one person enters per authentication cycle, eliminating the social engineering vector where an employee holds the door for an unauthorized individual.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which TWO of the following are effective physical security controls to prevent tailgating?
hardWhy B: A mantrap is a physical security control consisting of two interlocking doors that create a small vestibule. Only one door can be opened at a time, and the system verifies that only one person enters before allowing the second door to open. This design directly prevents tailgating by trapping unauthorized individuals who attempt to follow an authorized person through the first door.
Last reviewed: Jun 11, 2026
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