The answer is a TCP SYN scan on ports 80 and 443. This technique is the most appropriate for efficient host discovery because it targets the two most commonly open web service ports, allowing you to identify live hosts with minimal traffic while avoiding the noise of a full port scan. Unlike ICMP echo requests, which many modern firewalls block, a TCP SYN scan sends a single SYN packet and waits for a SYN-ACK response, making it stealthier and more reliable across routed subnets where ARP is limited to the local broadcast domain. On the CompTIA PenTest+ PT0-002 exam, this question tests your ability to balance stealth and efficiency in large-scale reconnaissance, often appearing as a trap where candidates mistakenly choose ICMP or ARP scans. Remember the memory tip: “80 and 443 keep the noise low—SYN is the way to go.”
PT0-002 Practice Question: Information Gathering and Vulnerability Scanning
This PT0-002 practice question tests your understanding of information gathering and vulnerability 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 is tasked with identifying live hosts on a large subnet without generating excessive traffic. Which of the following techniques is most appropriate for efficient host discovery?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
TCP SYN scan on port 80 and 443
A TCP SYN scan on ports 80 and 443 is the most appropriate technique because it targets common web service ports, which are often open on live hosts, and generates minimal traffic compared to a full port scan. Unlike ICMP or ARP scans, a TCP SYN scan can bypass firewalls that block ICMP echo requests and is effective across routed subnets where ARP is limited to the local broadcast domain. This approach balances stealth and efficiency for large-scale host discovery.
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.
✗
ARP scan
Why it's wrong here
ARP scan only works on the local subnet and is not suitable for remote networks.
✓
TCP SYN scan on port 80 and 443
Why this is correct
These ports are commonly open on servers; SYN scan is lightweight and effective.
Related concept
Read the scenario before looking for a memorised answer.
✗
DNS zone transfer
Why it's wrong here
DNS zone transfer is used for enumerating domain records, not host discovery.
✗
ICMP echo sweep
Why it's wrong here
ICMP is often blocked by firewalls, and sweeps generate noticeable traffic.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose ICMP echo sweep (Option D) because they associate 'ping' with host discovery, but fail to consider that ICMP is frequently blocked by firewalls, making TCP SYN scans on common ports a more reliable and stealthier alternative in modern networks.
Detailed technical explanation
How to think about this question
A TCP SYN scan sends a SYN packet to the target port; if a SYN-ACK is received, the host is live and the port is open, and the scanner responds with a RST to avoid completing the handshake. This technique is part of the TCP half-open scan family and is favored for its low overhead and ability to bypass simple packet filters that do not inspect TCP flags. In real-world engagements, scanning only ports 80 and 443 is a common reconnaissance tactic because these ports are almost universally allowed outbound and often open on web servers, reducing false negatives.
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 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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this PT0-002 question in full detail.
Information Gathering and Vulnerability Scanning — This question tests Information Gathering and Vulnerability Scanning — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: TCP SYN scan on port 80 and 443 — A TCP SYN scan on ports 80 and 443 is the most appropriate technique because it targets common web service ports, which are often open on live hosts, and generates minimal traffic compared to a full port scan. Unlike ICMP or ARP scans, a TCP SYN scan can bypass firewalls that block ICMP echo requests and is effective across routed subnets where ARP is limited to the local broadcast domain. This approach balances stealth and efficiency for large-scale host discovery.
What should I do if I get this PT0-002 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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