- A
Perform a UDP scan on the four specified ports and identify running services
Why wrong: -sS is a TCP SYN scan, not a UDP scan. UDP scanning requires the -sU flag.
- B
Perform an aggressive scan of all open ports and enumerate SMB shares
Why wrong: The -A flag enables aggressive mode (not used here). SMB enumeration requires specific scripts (--script smb-enum-shares). The specified ports do not include 445.
- C
Perform a TCP SYN scan on four ports, detect service versions, and attempt OS fingerprinting
-sS = SYN/stealth scan, -sV = version detection, -O = OS fingerprinting, -p 22,80,443,3389 = scan only these four ports. This is a targeted reconnaissance scan.
- D
Perform a full TCP connect scan with UDP service detection on all ports
Why wrong: -sS is a SYN scan, not a full connect scan. -sV detects TCP service versions, not UDP. Not all ports are specified.
CEH Footprinting, Reconnaissance and Scanning Practice Question
This CEH practice question tests your understanding of footprinting, reconnaissance and scanning. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 runs the following Nmap command: nmap -sS -sV -O -p 22,80,443,3389 192.168.1.0/24. Which of the following BEST describes what this scan will accomplish?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
Perform a TCP SYN scan on four ports, detect service versions, and attempt OS fingerprinting
Option C is correct because the command uses the -sS flag for a TCP SYN scan (stealth scan), -sV for service version detection, and -O for OS fingerprinting, targeting only the four specified ports (22, 80, 443, 3389) across the 192.168.1.0/24 subnet. This combination performs a half-open TCP scan on those ports, probes open ports to identify service versions, and attempts to determine the operating system based on TCP/IP stack responses.
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.
- ✗
Perform a UDP scan on the four specified ports and identify running services
- ✗
Perform an aggressive scan of all open ports and enumerate SMB shares
Why it's wrong here
The -A flag enables aggressive mode (not used here). SMB enumeration requires specific scripts (--script smb-enum-shares). The specified ports do not include 445.
- ✓
Perform a TCP SYN scan on four ports, detect service versions, and attempt OS fingerprinting
Why this is correct
-sS = SYN/stealth scan, -sV = version detection, -O = OS fingerprinting, -p 22,80,443,3389 = scan only these four ports. This is a targeted reconnaissance scan.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Perform a full TCP connect scan with UDP service detection on all ports
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the -sS (SYN scan) with -sT (TCP connect scan) or -sU (UDP scan), and they may incorrectly assume that -sV and -O automatically scan all ports or perform additional enumeration like SMB sharing, when in fact the port range is explicitly limited by the -p option.
Detailed technical explanation
How to think about this question
The TCP SYN scan (-sS) sends a SYN packet and waits for a SYN-ACK (open) or RST (closed), never completing the three-way handshake, making it stealthier than a connect scan. The -O flag uses techniques like TCP timestamp option, initial sequence number prediction, and IP ID sampling to fingerprint the OS, but it requires at least one open and one closed port for accurate results; if only these four ports are all open or all filtered, OS detection may be less reliable. In real-world scenarios, scanning a /24 subnet with these flags on only four ports is efficient for identifying critical services (SSH, HTTP, HTTPS, RDP) and their versions, but it may miss other services on non-standard ports.
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
Got this wrong? Here's your next step.
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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: Perform a TCP SYN scan on four ports, detect service versions, and attempt OS fingerprinting — Option C is correct because the command uses the -sS flag for a TCP SYN scan (stealth scan), -sV for service version detection, and -O for OS fingerprinting, targeting only the four specified ports (22, 80, 443, 3389) across the 192.168.1.0/24 subnet. This combination performs a half-open TCP scan on those ports, probes open ports to identify service versions, and attempts to determine the operating system based on TCP/IP stack responses.
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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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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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