The answer is to implement a mantrap with two interlocking doors at the entrance. This physical control directly addresses the vulnerability of tailgating and door propping by creating a small vestibule where only one person can authenticate and enter per card swipe, effectively isolating each individual before the second door unlocks. On the CISSP exam, this question tests your understanding of the difference between preventive and detective controls within physical security; a mantrap is a classic preventive measure, whereas a camera or alarm is merely detective. A common trap is to choose a biometric reader, which strengthens authentication but does nothing to stop a propped door or unauthorized followers. Remember the memory tip: "Mantrap stops the tailgate, not just the password."
CISSP Security Operations Practice Question
This CISSP practice question tests your understanding of security operations. 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 the security manager for a manufacturing company with a large facility that houses production servers and sensitive intellectual property. The facility has a single physical entrance that uses a card reader for access control. During a routine audit, you find that the door prop alarm has been bypassed by taping a magnet to the sensor, allowing the door to stay open without triggering an alert. The security guard station is located 200 feet away and does not have a direct line of sight to the door. Which control should you implement FIRST to prevent unauthorized physical access?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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 two interlocking doors at the entrance.
Option B is the most effective and immediate physical control: a mantrap prevents tailgating and ensures only one person enters per card swipe. Option A (video camera) is detective, not preventive. Option C (security patrol) is resource-intensive and reactive. Option D (biometric reader) adds authentication but does not prevent door propping or tailgating.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Replace the card reader with a biometric fingerprint scanner.
Why it's wrong here
Biometrics strengthen authentication but do not prevent door propping.
✗
Increase the frequency of security patrols around the entrance.
Why it's wrong here
Patrols are reactive and may not catch doors propped open in time.
✓
Implement a mantrap with two interlocking doors at the entrance.
Why this is correct
A mantrap physically prevents unauthorized access and tailgating.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
Install a video surveillance camera to monitor the entrance.
Why it's wrong here
Camera only records incidents, does not prevent them.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A security team runs a vulnerability scan on a web application and discovers an unpatched SQL injection flaw. The team prioritises remediation by CVSS score — critical flaws are patched within 24 hours, high within 7 days. Questions like this test whether you understand vulnerability management processes, scanning tools, and remediation prioritisation.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CISSP NAT questions on configuration and troubleshooting.
Security Operations — This question tests Security Operations — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Implement a mantrap with two interlocking doors at the entrance. — Option B is the most effective and immediate physical control: a mantrap prevents tailgating and ensures only one person enters per card swipe. Option A (video camera) is detective, not preventive. Option C (security patrol) is resource-intensive and reactive. Option D (biometric reader) adds authentication but does not prevent door propping or tailgating.
What should I do if I get this CISSP question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related CISSP NAT questions on configuration and troubleshooting.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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