The answer is that the second scan identifies the version of the SSH service running on port 22. This is correct because the `-sV` flag enables Nmap service version detection, which actively probes open ports to determine the exact application and version, such as OpenSSH 5.3p1, rather than just confirming the port is open. On the Certified Ethical Hacker CEH exam, this tests your ability to distinguish between OS detection (`-O`), which fingerprints the operating system from network stack behavior, and service version detection (`-sV`), which reveals the software behind the port. A common trap is confusing `-sV` with OS fingerprinting or assuming it checks firewall rules—it does neither. Remember: `-O` tells you the *platform*, `-sV` tells you the *program*. A useful memory tip is to think of `-sV` as “service version,” where the ‘V’ stands for the version number you’re after.
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.
A penetration tester uses the following Nmap command: nmap -sS -O -p 1-1000 10.0.0.1. The output shows port 22 as open, and OS detection suggests 'Linux 2.6.x'. The tester then runs: nmap -sV -p 22 10.0.0.1. What additional information does the second scan provide?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It identifies the version of the SSH service running
The second scan uses the `-sV` flag, which enables version detection. Nmap probes the open port 22 (SSH) to determine the exact service version (e.g., OpenSSH 5.3p1). This is distinct from OS detection (`-O`), which guesses the operating system based on TCP/IP stack fingerprinting. The `-sV` scan provides granular service version information, not OS confirmation or firewall status.
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.
✗
It confirms the OS is Linux 2.6.x
Why it's wrong here
OS detection already identified the OS; -sV is for service versions.
✗
It checks if the port is filtered by a firewall
Why it's wrong here
Version scanning does not determine filtering; it only identifies the service version.
✓
It identifies the version of the SSH service running
Why this is correct
-sV performs version detection on the specified port.
Related concept
Read the scenario before looking for a memorised answer.
✗
It performs a UDP scan on port 22
Why it's wrong here
UDP scan requires -sU; -sV on a TCP port is still TCP.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing OS detection (`-O`) with service version detection (`-sV`), leading candidates to think `-sV` confirms the OS when it actually identifies the application version running on the port.
Detailed technical explanation
How to think about this question
Under the hood, `-sV` works by completing a TCP three-way handshake (if the port is open) and then sending a series of probes (e.g., NULL, FIN, or application-specific payloads) to elicit a response from the service. Nmap compares the response against a database of service fingerprints (nmap-service-probes) to identify the exact version. In real-world scenarios, knowing the SSH version helps identify vulnerable software (e.g., OpenSSH < 7.4 with CVE-2016-10009) or misconfigurations, which is critical for penetration testing.
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: It identifies the version of the SSH service running — The second scan uses the `-sV` flag, which enables version detection. Nmap probes the open port 22 (SSH) to determine the exact service version (e.g., OpenSSH 5.3p1). This is distinct from OS detection (`-O`), which guesses the operating system based on TCP/IP stack fingerprinting. The `-sV` scan provides granular service version information, not OS confirmation or firewall status.
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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