The answer is to run a TCP SYN scan on port 22 only, with version detection enabled, across the target IP range. This approach minimizes disruption while scanning for vulnerable OpenSSH because a SYN scan, often called a half-open scan, never completes the full TCP handshake, drastically reducing the chance of crashing services or triggering IDS alerts, and targeting only port 22 avoids flooding the network with unnecessary probe traffic. On the Certified Ethical Hacker CEH exam, this question tests your understanding of stealth scanning techniques versus full connect scans, with a common trap being the impulse to scan all ports for thoroughness—which wastes bandwidth and risks disruption. The key is that version detection, not just port discovery, is essential to confirm the specific vulnerable OpenSSH build. Memory tip: think “SYN-22-Version” as your three-step recipe for a quiet, accurate hunt.
CEH Scanning Networks and Enumeration Practice Question
This CEH practice question tests your understanding of scanning networks and enumeration. 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.
A network administrator needs to identify all devices on a large corporate network that are running a specific vulnerable version of OpenSSH. The administrator has network access and can use scanning tools. However, scanning the entire network might disrupt operations. Which approach minimizes disruption while accurately identifying the vulnerable hosts?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Run a TCP SYN scan on port 22 only, with version detection enabled, across the target IP range.
Option B is correct because it targets only TCP port 22 (the default SSH port) with a SYN scan, which is stealthier and faster than a full connect scan, and enables version detection to identify the specific vulnerable OpenSSH version. This minimizes disruption by avoiding scanning unnecessary ports and reduces network load, while accurately pinpointing vulnerable hosts.
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.
✗
Conduct a full TCP port scan of the entire network using SYN scan.
Why it's wrong here
Full port scans are noisy and may cause performance issues on network devices.
✓
Run a TCP SYN scan on port 22 only, with version detection enabled, across the target IP range.
Why this is correct
Scanning only the relevant port with version detection minimizes traffic and focuses on the vulnerable service.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use a ping sweep to identify live hosts, then perform a version scan on each.
Why it's wrong here
Ping sweep is less disruptive but still requires probing each live host; version scan still needed.
✗
Perform an ARP scan of the entire subnet and then check each host manually.
Why it's wrong here
Manual checking is inefficient and still requires direct interaction with each host.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose a ping sweep (Option C) thinking it reduces disruption, but they overlook that ICMP may be blocked, and the subsequent version scan on each host still requires port-level scanning, making Option B more efficient and accurate.
Detailed technical explanation
How to think about this question
A SYN scan (half-open scan) sends a TCP SYN packet to port 22; if a SYN-ACK is received, the host is listening, and the scanner sends an RST to avoid completing the handshake, reducing log noise. Version detection uses banner grabbing or SSH protocol negotiation to extract the exact OpenSSH version string (e.g., 'SSH-2.0-OpenSSH_7.4'), allowing precise identification of vulnerable builds without requiring a full connection.
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 network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Scanning Networks and Enumeration — This question tests Scanning Networks and Enumeration — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Run a TCP SYN scan on port 22 only, with version detection enabled, across the target IP range. — Option B is correct because it targets only TCP port 22 (the default SSH port) with a SYN scan, which is stealthier and faster than a full connect scan, and enables version detection to identify the specific vulnerable OpenSSH version. This minimizes disruption by avoiding scanning unnecessary ports and reduces network load, while accurately pinpointing vulnerable hosts.
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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