Question 437 of 1,000

Information Gathering and Vulnerability Scanning →hardMultiple ChoiceObjective-mapped

PT0-002 Practice Question: Information Gathering and Vulnerability Scanning

This PT0-002 practice question tests your understanding of information gathering and vulnerability scanning. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 conducting active reconnaissance and wants to perform a SYN scan on a target network. During the scan, the tester notices that some ports are reported as filtered. What does a filtered port status typically indicate in Nmap?

A
The port is closed and the target responded with a RST packet.
Why wrong: A closed port responds with RST, and Nmap reports it as 'closed', not filtered.
B
The port is open but no service is listening.
Why wrong: An open port with no service would be reported as 'open' with no service detected, not filtered.
C
The target is not responding to any probes.
Why wrong: If the target is not responding, Nmap may report the host as down or all ports as filtered, but filtered specifically means a firewall is interfering.
D
A firewall is blocking the probe packets.
Filtered ports typically result from firewall rules dropping or rejecting packets, preventing Nmap from determining the port state.

Full breakdown with real-world context →

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

✓

A firewall is blocking the probe packets.

Filtered ports in Nmap indicate that a firewall, packet filter, or other network obstacle is blocking the probe packets, preventing Nmap from determining whether the port is open or closed.

Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
The port is closed and the target responded with a RST packet.
Why it's wrong here
A closed port responds with RST, and Nmap reports it as 'closed', not filtered.
✗
The port is open but no service is listening.
Why it's wrong here
An open port with no service would be reported as 'open' with no service detected, not filtered.
✗
The target is not responding to any probes.
Why it's wrong here
If the target is not responding, Nmap may report the host as down or all ports as filtered, but filtered specifically means a firewall is interfering.
✓
A firewall is blocking the probe packets.
Why this is correct
Filtered ports typically result from firewall rules dropping or rejecting packets, preventing Nmap from determining the port state.
Related concept
Standard ACLs match source addresses.

Common exam traps

Common exam trap: ACLs stop at the first match

ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.

Detailed technical explanation

How to think about this question

ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.

KKey Concepts to Remember

Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.

TExam Day Tips

Check inbound versus outbound direction.
Read the ACL from top to bottom.
Look for a broader permit or deny above the intended line.

Key takeaway

ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.

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.

Visual reference

What to study next

Got this wrong? Here's your next step.

Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PT0-002 ACL questions on filtering logic and placement.

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FAQ

Questions learners often ask

What does this PT0-002 question test?

Information Gathering and Vulnerability Scanning — This question tests Information Gathering and Vulnerability Scanning — Standard ACLs match source addresses..

What is the correct answer to this question?

The correct answer is: A firewall is blocking the probe packets. — Filtered ports in Nmap indicate that a firewall, packet filter, or other network obstacle is blocking the probe packets, preventing Nmap from determining whether the port is open or closed.

What should I do if I get this PT0-002 question wrong?

What is the key concept behind this question?

Standard ACLs match source addresses.

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Last reviewed: Jul 4, 2026

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