The answer is the A record, which maps a hostname to an IPv4 address and is a primary target during DNS records subdomain enumeration. When a penetration tester queries A records for known or brute-forced hostnames like admin.example.com or mail.example.com, a valid response reveals an active subdomain and its IP address, effectively expanding the attack surface. On the CompTIA PenTest+ PT0-002 exam, this technique tests your understanding of passive and active reconnaissance phases—specifically how DNS enumeration uncovers hidden assets without direct interaction. A common trap is overlooking that A records can also be used in reverse lookups to find additional hostnames sharing the same IP. For the exam, remember that any record returning an IP address (A or AAAA) is your friend for subdomain discovery, while records like MX or NS reveal infrastructure but not direct hostnames. Memory tip: “A is for Address, and Addresses reveal Assets.”
PT0-002 Practice Question: Information Gathering and Vulnerability Scanning
This PT0-002 practice question tests your understanding of information gathering and vulnerability scanning. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 performing information gathering using DNS enumeration. Which of the following records can be queried to discover additional subdomains or hostnames? (Choose three.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
MX
The A record maps a hostname to an IPv4 address. During DNS enumeration, querying A records for known subdomains or performing a brute-force of common hostnames (e.g., admin.example.com, mail.example.com) can reveal additional subdomains and hostnames by returning valid IP addresses. This is a standard technique in reconnaissance to expand the attack surface.
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.
✓
MX
Why this is correct
MX records disclose mail exchange servers, which can be additional hostnames.
Related concept
Read the scenario before looking for a memorised answer.
✓
NS
Why this is correct
NS records reveal name servers, which may host many subdomains and allow zone transfers.
Related concept
Read the scenario before looking for a memorised answer.
✗
PTR
Why it's wrong here
PTR records are for reverse lookup; they map IPs to hostnames but are less likely to reveal new subdomains.
✓
A
Why this is correct
A records provide IP addresses of hostnames, and reverse lookups can reveal additional subdomains.
Related concept
Read the scenario before looking for a memorised answer.
✗
CNAME
Why it's wrong here
CNAME records are aliases and usually point to already known canonical names.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often think PTR records are useful for forward DNS enumeration, but they require a known IP and are used in reverse lookups, not for discovering subdomains from a domain name.
Detailed technical explanation
How to think about this question
DNS zone transfers (AXFR) are a more aggressive enumeration method, but when restricted, attackers often use dictionary or brute-force queries against A, MX, and NS records. MX records reveal mail server hostnames (e.g., mail.example.com), and NS records reveal authoritative name server hostnames (e.g., ns1.example.com), both of which can be queried for A records to find additional IP addresses and subdomains. Tools like dnsrecon and fierce automate this process by iterating through common subdomain wordlists.
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 analyst at a medium-sized enterprise encounters this scenario during an investigation or architecture review. The correct answer reflects best practice for the specific threat or control described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Security exam questions test whether you can match controls to threats in context — not just recall definitions.
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: MX — The A record maps a hostname to an IPv4 address. During DNS enumeration, querying A records for known subdomains or performing a brute-force of common hostnames (e.g., admin.example.com, mail.example.com) can reveal additional subdomains and hostnames by returning valid IP addresses. This is a standard technique in reconnaissance to expand the attack surface.
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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