- A
The server is using a reverse proxy that presents a different version to Nmap
Why wrong: If a reverse proxy were involved, Nmap might see the proxy's version, but banner grabbing from the same IP should match.
- B
Netcat banner grabbing is more reliable because it reads the actual server response
Netcat establishes a TCP connection and reads the service banner directly, while Nmap's -sV uses a database of signatures that may be incomplete or outdated.
- C
The discrepancy is due to Nmap's OS fingerprinting conflicting with version detection
Why wrong: OS fingerprinting (-O) does not affect service version detection (-sV). They are separate modules.
- D
Nmap is more accurate because it uses deep packet inspection
Why wrong: Banner grabbing directly reads the server's response, which is typically more accurate for version detection.
Quick Answer
The answer is that Netcat banner grabbing is more reliable than Nmap for version detection because it reads the actual server response directly. While Nmap’s -sV flag performs probe-response matching against its internal signature database, that database can be outdated or fail to recognize a newer service version, leading to a false lower version like 2.4.29 instead of the true 2.4.41. Netcat, by contrast, establishes a raw TCP connection and captures the unfiltered banner the server sends, making it the most immediate and accurate method for version identification. On the Certified Ethical Hacker CEH exam, this scenario tests your understanding of how Nmap’s version detection can be fooled by banner obfuscation or database gaps, while Netcat provides ground truth. A common trap is assuming Nmap is always correct because it is automated; remember that Nmap guesses, Netcat reads. Memory tip: “Nmap probes, Netcat quotes”—the tool that quotes the server’s own words wins.
CEH Footprinting, Reconnaissance and Scanning Practice Question
This CEH practice question tests your understanding of footprinting, reconnaissance and scanning. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
During a penetration test, you run the following Nmap command: nmap -sS -sV -O -A -T4 --script=default 10.0.0.1. The scan results show that port 443 is open and the service is 'Apache httpd 2.4.29'. However, banner grabbing with Netcat shows 'Apache/2.4.41 (Ubuntu)'. What is the MOST likely explanation for the discrepancy?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
Netcat banner grabbing is more reliable because it reads the actual server response
Option B is correct because Netcat performs a direct TCP connection to the service and reads the raw banner as sent by the application, which is the most immediate and unfiltered version information. Nmap's version detection (-sV) relies on probe-response matching against its signature database, which can be outdated or misinterpret the service if the server uses banner obfuscation or if the Nmap database does not have an exact match for the newer version. In this case, Netcat reveals the actual server version (2.4.41), while Nmap's database may only have a signature for 2.4.29, leading to a false lower version.
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.
- ✗
The server is using a reverse proxy that presents a different version to Nmap
Why it's wrong here
If a reverse proxy were involved, Nmap might see the proxy's version, but banner grabbing from the same IP should match.
- ✓
Netcat banner grabbing is more reliable because it reads the actual server response
Why this is correct
Netcat establishes a TCP connection and reads the service banner directly, while Nmap's -sV uses a database of signatures that may be incomplete or outdated.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The discrepancy is due to Nmap's OS fingerprinting conflicting with version detection
Why it's wrong here
OS fingerprinting (-O) does not affect service version detection (-sV). They are separate modules.
- ✗
Nmap is more accurate because it uses deep packet inspection
Why it's wrong here
Banner grabbing directly reads the server's response, which is typically more accurate for version detection.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume Nmap is always more accurate because it is a sophisticated scanning tool, but in version detection, a direct banner grab with Netcat is often more reliable when the service banner is not suppressed.
Detailed technical explanation
How to think about this question
Nmap's service version detection works by sending a series of probes (e.g., NULL, Generic, SSL/TLS) and comparing the responses to a database of known service fingerprints. If the server's response does not exactly match any fingerprint, Nmap may fall back to a generic match or an older version. Netcat, on the other hand, simply connects and reads the initial banner as defined in RFC 2616 for HTTP, which is the raw server string. In real-world scenarios, administrators may configure Apache to hide the exact version in the banner (e.g., ServerTokens Prod), but here the banner is explicit, making Netcat's result the ground truth.
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 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
Questions learners often ask
What does this CEH question test?
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: Netcat banner grabbing is more reliable because it reads the actual server response — Option B is correct because Netcat performs a direct TCP connection to the service and reads the raw banner as sent by the application, which is the most immediate and unfiltered version information. Nmap's version detection (-sV) relies on probe-response matching against its signature database, which can be outdated or misinterpret the service if the server uses banner obfuscation or if the Nmap database does not have an exact match for the newer version. In this case, Netcat reveals the actual server version (2.4.41), while Nmap's database may only have a signature for 2.4.29, leading to a false lower version.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This CEH practice question is part of Courseiva's free EC-Council 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 CEH exam.
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