Quick Answer
The answer is the Nmap SYN scan flag -sS, which produced the output showing open ports and their service names. This flag initiates a stealthy half-open TCP scan that sends SYN packets without completing the three-way handshake, allowing it to identify open ports while avoiding full connection logs. The output format—listing port numbers, states, and service names like ssh, http, and https—matches exactly what -sS returns by default, as it maps port numbers to service names from the /etc/services file without performing version detection or OS fingerprinting. On the Certified Ethical Hacker CEH exam, this question tests your ability to distinguish between scan types: -sS is the default and most common scan, often contrasted with -sT (full connect) or -sV (version detection). A common trap is confusing the service name output with version information; remember that -sS gives service names only, not versions. Memory tip: “SYN Stealth Shows Services”—the double S in -sS stands for both SYN and Stealth, and the output shows service names, not versions.
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 is scanning a target and receives the output: 'PORT STATE SERVICE 22/tcp open ssh 80/tcp open http 443/tcp open https'. Which Nmap flag was MOST likely used to obtain this output?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
-sS
-sS performs a SYN scan and displays open ports with service names.
-O
Why wrong: -O adds OS detection, which is not shown here.
-A
Why wrong: -A enables aggressive scanning including OS detection and version detection, which would show more details.
-sV
Why wrong: -sV would show version details like 'OpenSSH 7.4', not just service names.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
-sS
The output shows open ports with their service names (ssh, http, https) but no version information. The -sS flag performs a SYN stealth scan, which by default probes common ports and uses the /etc/services file to map port numbers to service names. This matches the output format exactly, as -sS does not perform version detection or OS fingerprinting.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
-sS
Why this is correct
-sS performs a SYN scan and displays open ports with service names.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
-O
Why it's wrong here
-O adds OS detection, which is not shown here.
-A
Why it's wrong here
-A enables aggressive scanning including OS detection and version detection, which would show more details.
-sV
Why it's wrong here
-sV would show version details like 'OpenSSH 7.4', not just service names.
Common exam traps
The trap here is that candidates often confuse the service name mapping (from -sS or default scan) with version detection (-sV), assuming that seeing 'ssh' or 'http' implies version probing occurred, when in fact Nmap simply maps the port number to a common service name from its database.
Trap categories for this question
Command / output trap
-O adds OS detection, which is not shown here.
Detailed technical explanation
Nmap's -sS sends SYN packets and analyzes responses to determine port states without completing the TCP handshake, making it stealthy and fast. The service names shown come from Nmap's nmap-services file (a compiled database of port-to-service mappings), not from actual service interrogation. In real-world scenarios, a penetration tester might use -sS first for a quick port discovery, then follow up with -sV to confirm service versions and identify potential vulnerabilities.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Footprinting, Reconnaissance and Scanning — This question tests Footprinting, Reconnaissance and Scanning — Read the scenario before looking for a memorised answer..
The correct answer is: -sS — The output shows open ports with their service names (ssh, http, https) but no version information. The -sS flag performs a SYN stealth scan, which by default probes common ports and uses the /etc/services file to map port numbers to service names. This matches the output format exactly, as -sS does not perform version detection or OS fingerprinting.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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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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