- A
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.
- B
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.
- C
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.
- D
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.
Quick Answer
The correct answer is that this Nmap command performs a TCP SYN scan on four ports, detects service versions, and attempts OS fingerprinting. This is because the `-sS` flag initiates a stealth half-open scan that never completes the TCP handshake, `-sV` probes open ports to identify running application versions, and `-O` sends a series of probes to guess the target operating system; the `-p` option limits the scan to ports 22, 80, 443, and 3389, while the `/24` subnet targets all 256 hosts in the 192.168.1.0 range. On the CEH exam, this combination tests your ability to read multi-flag Nmap syntax and understand how each flag modifies scan behavior—a common trap is confusing `-sS` with a full connect scan (`-sT`) or forgetting that `-O` requires root privileges for accurate results. To remember the flags, think “SSVO” as “Stealth, Service, Version, OS”—each letter maps directly to the scan’s purpose.
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 security analyst 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 B is correct because the `-sS` flag initiates a TCP SYN stealth scan, `-sV` enables service version detection, and `-O` attempts OS fingerprinting. The `-p 22,80,443,3389` limits the scan to those four ports, and the target `192.168.1.0/24` scans the entire Class C subnet. This combination performs a half-open scan on the specified ports, probes for application versions, and tries to identify the operating system of each live host.
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 full TCP connect scan with UDP service detection on all ports
- ✓
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 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 UDP scan on the four specified ports and identify running services
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse `-sS` (SYN scan) with a full connect scan (`-sT`) or mistakenly think `-sV` and `-O` imply an aggressive scan (`-A`), which also includes default scripts and traceroute.
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, which avoids logging on some systems. Service version detection (`-sV`) sends probes to open ports and matches responses against a signature database, while OS fingerprinting (`-O`) analyzes TCP/IP stack behaviors like TTL, window size, and initial sequence numbers. In a real-world scenario, this scan is ideal for initial reconnaissance of a subnet to identify live hosts, their services, and OS types without generating excessive noise.
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 B is correct because the `-sS` flag initiates a TCP SYN stealth scan, `-sV` enables service version detection, and `-O` attempts OS fingerprinting. The `-p 22,80,443,3389` limits the scan to those four ports, and the target `192.168.1.0/24` scans the entire Class C subnet. This combination performs a half-open scan on the specified ports, probes for application versions, and tries to identify the operating system of each live host.
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
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
2 more ways this is tested on CEH
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A security analyst 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?
medium- A.Perform an aggressive scan of all open ports and enumerate SMB shares
- ✓ B.Perform a TCP SYN scan on four ports, detect service versions, and attempt OS fingerprinting
- C.Perform a UDP scan on the four specified ports and identify running services
- D.Perform a full TCP connect scan with UDP service detection on all ports
Why B: Option B is correct because the command `nmap -sS -sV -O -p 22,80,443,3389 192.168.1.0/24` performs a TCP SYN scan (`-sS`) on only the four specified ports, enables service version detection (`-sV`), and attempts OS fingerprinting (`-O`). This is a stealthy half-open scan that does not complete the TCP three-way handshake, combined with banner grabbing and OS detection, limited to the given port list.
Variation 2. 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?
medium- A.Perform a UDP scan on the four specified ports and identify running services
- B.Perform an aggressive scan of all open ports and enumerate SMB shares
- ✓ C.Perform a TCP SYN scan on four ports, detect service versions, and attempt OS fingerprinting
- D.Perform a full TCP connect scan with UDP service detection on all ports
Why C: 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.
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Last reviewed: Jun 24, 2026
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