Quick Answer
The answer is `nmap -T5 -F target`, which is the most appropriate command for a penetration tester needing to quickly identify open ports among the top 100 common ports while minimizing network traffic and scan time. The `-F` flag, or fast mode, restricts scanning to only the 100 most frequently used ports defined in Nmap’s `nmap-services` file, while the `-T5` flag applies the “insane” timing template, aggressively reducing inter-probe delays and retransmission timeouts for maximum speed. On the CompTIA PenTest+ PT0-002 exam, this scenario tests your ability to balance efficiency with reconnaissance goals, often appearing in questions about stealth or time-constrained scans. A common trap is confusing `-F` with `--top-ports 100` (which achieves the same result but is less concise) or assuming `-T5` alone limits port count. Remember the mnemonic “Fast Five” to link `-F` (fast ports) with `-T5` (fast timing) for a rapid, low-traffic scan.
This PT0-002 practice question tests your understanding of information gathering and vulnerability scanning. Compare every option against the stated constraints before choosing — the best answer satisfies all requirements, not just the most obvious one. 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 wants to quickly identify which of the top 100 common ports are open on a target system, while minimizing network traffic and scan time. Which Nmap command is most appropriate?
nmap -p- target
Why wrong: This scans all 65535 ports, which takes significant time and generates more traffic.
nmap -T5 -F target
-F scans top 100 ports; -T5 uses aggressive timing for speed.
nmap -sn target
Why wrong: -sn performs a ping scan to see which hosts are up, not port scanning.
nmap -sV target
Why wrong: -sV performs version detection, which is slower and not focused on top ports only.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
nmap -T5 -F target
Option B is correct because the `-T5` flag sets the fastest timing template (insane), which reduces delays and speeds up the scan, while the `-F` flag (fast mode) limits scanning to only the top 100 most common ports as defined in Nmap's nmap-services file. This combination minimizes network traffic and scan time while quickly identifying open ports among the top 100, aligning with the goal of efficiency.
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.
nmap -p- target
Why it's wrong here
This scans all 65535 ports, which takes significant time and generates more traffic.
nmap -T5 -F target
Why this is correct
-F scans top 100 ports; -T5 uses aggressive timing for speed.
Related concept
Read the scenario before looking for a memorised answer.
nmap -sn target
Why it's wrong here
-sn performs a ping scan to see which hosts are up, not port scanning.
nmap -sV target
Why it's wrong here
-sV performs version detection, which is slower and not focused on top ports only.
Common exam traps
The trap here is that candidates often confuse `-F` with `-p-` or assume `-T5` alone is sufficient, failing to recognize that `-F` is the specific flag that restricts the scan to the top 100 ports, while `-T5` only accelerates the timing without changing the port list.
Detailed technical explanation
Nmap's `-F` flag reduces the port list from the default 1000 ports to the top 100 ports based on frequency in the nmap-services file, which is derived from empirical data across millions of scans. The `-T5` timing template sets the `min_rtt_timeout` to 50ms, `max_rtt_timeout` to 300ms, and `initial_rtt_timeout` to 50ms, along with a 5ms probe delay, aggressively reducing wait times but risking packet loss or incomplete results on unreliable networks. In real-world engagements, this combination is useful for a quick reconnaissance pass, but the tester must be aware that `-T5` may miss hosts or ports due to dropped packets, especially over high-latency links.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A security team runs a vulnerability scan on a web application and discovers an unpatched SQL injection flaw. The team prioritises remediation by CVSS score — critical flaws are patched within 24 hours, high within 7 days. Questions like this test whether you understand vulnerability management processes, scanning tools, and remediation prioritisation.
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
Information Gathering and Vulnerability Scanning — This question tests Information Gathering and Vulnerability Scanning — Read the scenario before looking for a memorised answer..
The correct answer is: nmap -T5 -F target — Option B is correct because the `-T5` flag sets the fastest timing template (insane), which reduces delays and speeds up the scan, while the `-F` flag (fast mode) limits scanning to only the top 100 most common ports as defined in Nmap's nmap-services file. This combination minimizes network traffic and scan time while quickly identifying open ports among the top 100, aligning with the goal of efficiency.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
This PT0-002 practice question is part of Courseiva's free CompTIA 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 PT0-002 exam.
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