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 discover subdomains of a target domain without sending any packets directly to the target's network. Which resource is most effective for this purpose?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Certificate Transparency logs
Certificate Transparency (CT) logs are publicly accessible, append-only ledgers that record every SSL/TLS certificate issued by a Certificate Authority (CA). Since certificates often include Subject Alternative Names (SANs) listing subdomains, querying CT logs (e.g., via crt.sh or tools like `certigo`) reveals subdomains without any direct network probes. This makes CT logs the most effective passive reconnaissance resource, as no packets are sent to the target's infrastructure.
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.
✗
DNS brute force with a wordlist
Why it's wrong here
DNS brute force sends many queries to DNS servers, which is active reconnaissance.
✓
Certificate Transparency logs
Why this is correct
These logs contain issued certificates which include subdomains; they can be queried passively.
Related concept
Read the scenario before looking for a memorised answer.
✗
WHOIS lookup
Why it's wrong here
WHOIS returns domain registration information but not internal subdomains.
✗
Traceroute
Why it's wrong here
Traceroute actively probes network paths and is not used for subdomain discovery.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between active and passive reconnaissance; the trap here is assuming DNS brute force is passive because it uses a wordlist, but it actively queries DNS servers, whereas CT logs are truly passive as they rely on publicly archived certificate data.
Detailed technical explanation
How to think about this question
CT logs are governed by RFC 6962 and are maintained by multiple log operators (e.g., Google, Cloudflare). Each log entry includes the certificate's serial number, issuer, validity period, and SANs. Tools like `crt.sh` aggregate data from multiple logs and allow filtering by domain, enabling discovery of subdomains that may not be indexed by search engines or DNS. A real-world scenario: a tester finds a staging subdomain (e.g., `dev.example.com`) via CT logs that is not in public DNS but has a valid certificate, revealing an attack surface.
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.
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: Certificate Transparency logs — Certificate Transparency (CT) logs are publicly accessible, append-only ledgers that record every SSL/TLS certificate issued by a Certificate Authority (CA). Since certificates often include Subject Alternative Names (SANs) listing subdomains, querying CT logs (e.g., via crt.sh or tools like `certigo`) reveals subdomains without any direct network probes. This makes CT logs the most effective passive reconnaissance resource, as no packets are sent to the target's infrastructure.
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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