- A
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.
- B
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.
- 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 scan performs a TCP SYN scan on four ports, detects service versions, and attempts OS fingerprinting. This is because the `-sS` flag initiates a stealthy half-open TCP SYN scan, which never completes the full handshake, making it less likely to be logged; `-sV` then probes any discovered open ports to determine the exact service and version running, while `-O` sends a series of TCP/IP probes to analyze the target’s stack behavior for OS fingerprinting. On the Certified Ethical Hacker CEH exam, this combination tests your understanding of reconnaissance techniques and the ability to interpret Nmap flags in a penetration testing scenario—a common trap is confusing `-sS` with a full connect scan (`-sT`) or forgetting that `-O` requires root privileges. Remember the mnemonic “SSVO” as in “Stealth, Service, Version, OS” to quickly recall the flag order and purpose.
CEH Enumeration and System Hacking Practice Question
This CEH practice question tests your understanding of enumeration and system hacking. 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. The -sS flag performs a TCP SYN (stealth) scan, -sV detects service versions, -O attempts OS fingerprinting, and -p restricts scanning to ports 22, 80, 443, and 3389. This combination identifies open ports, service versions, and OS on the target subnet.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 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
CIDR notation defines the prefix length.
- ✗
Perform a full TCP connect scan with UDP service detection on all ports
- ✗
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: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related CEH subnetting questions on CIDR, address ranges, and subnet selection.
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FAQ
Questions learners often ask
What does this CEH question test?
Enumeration and System Hacking — This question tests Enumeration and System Hacking — CIDR notation defines the prefix length..
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. The -sS flag performs a TCP SYN (stealth) scan, -sV detects service versions, -O attempts OS fingerprinting, and -p restricts scanning to ports 22, 80, 443, and 3389. This combination identifies open ports, service versions, and OS on the target subnet.
What should I do if I get this CEH question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related CEH subnetting questions on CIDR, address ranges, and subnet selection.
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?
CIDR notation defines the prefix length.
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Last reviewed: Jun 21, 2026
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