PT0-002 Practice Question: Passive DNS reconnaissance uses public resolvers.
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. A key principle to apply: passive DNS reconnaissance uses public resolvers.. 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.
During the reconnaissance phase, a penetration tester wants to map out the target's DNS infrastructure without directly interacting with the target's servers. Which of the following techniques BEST achieves this?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Querying publicly available DNS records
Option B is correct because querying publicly available DNS records (e.g., via passive DNS, WHOIS, or DNS dumpster) allows the tester to gather DNS information without any direct interaction with the target's servers. This technique relies on third-party databases and cached records, avoiding any packets sent to the target, which is essential for stealth during reconnaissance. It aligns with passive information gathering, as defined in the PT0-002 objectives.
Key principle: Passive DNS reconnaissance uses public resolvers.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Performing a DNS zone transfer
Why it's wrong here
A zone transfer is an active query to the target's DNS server and often restricted.
✓
Querying publicly available DNS records
Why this is correct
Using public DNS resolvers to retrieve records like A, MX, or CNAME is passive and avoids direct interaction.
Clue confirmation
The clue word "best" in the question point toward this answer.
Nmap scanning is an active technique that sends probes to the target network.
✗
Sending crafted DNS queries to the target's DNS server
Why it's wrong here
This is an active technique that directly interacts with the target's servers.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'passive reconnaissance' with 'active reconnaissance' and choose a technique like DNS zone transfer or Nmap scanning, which are clearly active and detectable, because they assume any DNS enumeration must involve direct queries.
Detailed technical explanation
How to think about this question
Passive DNS collection leverages distributed databases like SecurityTrails or VirusTotal that aggregate DNS resolution history from recursive resolvers, allowing testers to see historical A, MX, and NS records without querying the target. This technique is especially useful for discovering subdomains or legacy records that may no longer be in the target's current zone but still resolve, revealing forgotten attack surfaces. Under the hood, passive DNS relies on time-to-live (TTL) expiration and caching behaviors, which can sometimes yield stale data that active queries would not reveal.
KKey Concepts to Remember
Passive DNS reconnaissance uses public resolvers.
It avoids direct network interaction with the target.
Common records retrieved include A, MX, CNAME, and NS.
Tools like `dig` and `nslookup` can be used for public queries.
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
Passive DNS reconnaissance uses public resolvers.
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 — Passive DNS reconnaissance uses public resolvers..
What is the correct answer to this question?
The correct answer is: Querying publicly available DNS records — Option B is correct because querying publicly available DNS records (e.g., via passive DNS, WHOIS, or DNS dumpster) allows the tester to gather DNS information without any direct interaction with the target's servers. This technique relies on third-party databases and cached records, avoiding any packets sent to the target, which is essential for stealth during reconnaissance. It aligns with passive information gathering, as defined in the PT0-002 objectives.
What should I do if I get this PT0-002 question wrong?
Review passive DNS reconnaissance uses public resolvers., then practise related PT0-002 questions on the same topic to reinforce the concept.
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?
Passive DNS reconnaissance uses public resolvers.
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