CEH Footprinting, Reconnaissance and Scanning Practice Question
This CEH practice question tests your understanding of footprinting, reconnaissance and scanning. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A security analyst is conducting a vulnerability scan on a web server using Nessus. After the scan, they notice that the server's performance has degraded significantly, and some services have become unresponsive. Which of the following actions could have prevented this issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure Nessus to use a 'safe' scan policy that disables disruptive plugins
Option B is correct because Nessus 'safe' scan policies disable plugins known to cause service disruption, such as those performing denial-of-service tests or exploiting vulnerabilities that may crash services. By using a safe policy, the analyst avoids aggressive checks that can degrade server performance or cause unresponsiveness, which is a common risk during vulnerability scanning.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Increase the scan intensity to complete faster and reduce the load
Why it's wrong here
Increasing intensity would likely worsen performance issues, not prevent them.
✓
Configure Nessus to use a 'safe' scan policy that disables disruptive plugins
Why this is correct
Safe checks in Nessus avoid plugins known to cause denial of service or system crashes.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use a different scanner like OpenVAS which is less intrusive
Why it's wrong here
Both Nessus and OpenVAS have safe scan options; switching scanners alone does not guarantee reduced impact without proper configuration.
✗
Run the scan during peak hours to blend in with normal traffic
Why it's wrong here
Running during peak hours would add more load and could exacerbate performance degradation.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think using a different scanner (Option C) or adjusting timing (Option D) solves the problem, but the core issue is the use of disruptive plugins, which is directly controlled by the scan policy, not the scanner brand or schedule.
Detailed technical explanation
How to think about this question
Nessus safe scan policies exclude plugins categorized as 'destructive' or 'denial of service,' which often test for vulnerabilities like buffer overflows or resource exhaustion (e.g., CVE-2014-0160 Heartbleed safe checks). Under the hood, Nessus uses the NASL (Nessus Attack Scripting Language) to execute plugins; safe policies filter out scripts with the 'destructive' flag set to 'true.' In real-world scenarios, a misconfigured scan with aggressive plugins can crash a web server's Apache or IIS process, leading to downtime that could have been avoided by selecting a safe policy.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the CEH exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Footprinting, Reconnaissance and Scanning — This question tests Footprinting, Reconnaissance and Scanning — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure Nessus to use a 'safe' scan policy that disables disruptive plugins — Option B is correct because Nessus 'safe' scan policies disable plugins known to cause service disruption, such as those performing denial-of-service tests or exploiting vulnerabilities that may crash services. By using a safe policy, the analyst avoids aggressive checks that can degrade server performance or cause unresponsiveness, which is a common risk during vulnerability scanning.
What should I do if I get this CEH question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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