- A
Searching crt.sh (Certificate Transparency logs).
Certificate logs are public and contain SAN entries, making them an excellent source for passive subdomain enumeration. Tools like crt.sh or digicert can be queried.
- B
DNS zone transfer.
Why wrong: DNS zone transfer is an active technique that requires the target DNS server to allow it, which is rare due to security hardening. It also sends traffic to the target.
- C
Using Nmap to brute-force subdomains.
Why wrong: Nmap brute-force is an active method that sends numerous DNS queries to the target, generating traffic and potentially triggering alerts. It is not passive.
- D
Querying the domain's MX records.
Why wrong: MX records provide mail server information, not a comprehensive list of subdomains. It may reveal a few but is not effective for broad enumeration.
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 wants to identify all subdomains for a target domain using only public records. Which technique is most effective for this purpose?
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
Searching crt.sh (Certificate Transparency logs).
Certificate Transparency logs, accessible via crt.sh, are a public record of all SSL/TLS certificates issued for a domain. Since certificates often include Subject Alternative Names (SANs) listing subdomains, querying crt.sh reveals subdomains without any interaction with the target's infrastructure. This technique is passive, requires no authorization, and leverages mandatory logging per RFC 6962, making it highly effective for enumeration from public records.
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.
- ✓
Searching crt.sh (Certificate Transparency logs).
Why this is correct
Certificate logs are public and contain SAN entries, making them an excellent source for passive subdomain enumeration. Tools like crt.sh or digicert can be queried.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
DNS zone transfer.
Why it's wrong here
DNS zone transfer is an active technique that requires the target DNS server to allow it, which is rare due to security hardening. It also sends traffic to the target.
- ✗
Using Nmap to brute-force subdomains.
Why it's wrong here
Nmap brute-force is an active method that sends numerous DNS queries to the target, generating traffic and potentially triggering alerts. It is not passive.
- ✗
Querying the domain's MX records.
Why it's wrong here
MX records provide mail server information, not a comprehensive list of subdomains. It may reveal a few but is not effective for broad enumeration.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse 'public records' with 'active DNS queries' and choose DNS zone transfer (B) or brute-forcing (C), failing to recognize that Certificate Transparency logs are the only passive, public-record-based option listed.
Detailed technical explanation
How to think about this question
Certificate Transparency logs are append-only ledgers that certificate authorities (CAs) must submit certificates to, as mandated by Google's CT policy for publicly trusted TLS certificates. Tools like crt.sh query these logs via a REST API, returning JSON data that includes the `name_value` field containing all SANs and CNs. In real-world engagements, this often reveals hidden subdomains, staging environments, or internal services that are not listed in public DNS records, providing a stealthy reconnaissance vector.
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 developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
What to study next
Got this wrong? Here's your next step.
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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 — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Searching crt.sh (Certificate Transparency logs). — Certificate Transparency logs, accessible via crt.sh, are a public record of all SSL/TLS certificates issued for a domain. Since certificates often include Subject Alternative Names (SANs) listing subdomains, querying crt.sh reveals subdomains without any interaction with the target's infrastructure. This technique is passive, requires no authorization, and leverages mandatory logging per RFC 6962, making it highly effective for enumeration from public records.
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.
About these practice questions
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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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