Restricting zone transfers to authorized IP addresses is the correct choice because it directly prevents unauthorized DNS zone transfer attacks by ensuring only trusted secondary DNS servers can request a full copy of the zone data. This countermeasure works by configuring an allow-transfer list on the primary DNS server—such as using the 'allow-transfer { trusted_servers; };' directive in BIND—which rejects any zone transfer request from an IP not explicitly permitted, thereby blocking attackers from enumerating all DNS records. On the Certified Ethical Hacker CEH exam, this concept tests your understanding of DNS security fundamentals and often appears in questions about reconnaissance countermeasures; a common trap is confusing zone transfer prevention with disabling recursion or using TSIG, which serve different purposes. Remember the memory tip: “Allow only the IPs you trust, or the zone will be bust.”
CEH Footprinting, Reconnaissance and Scanning Practice Question
This CEH practice question tests your understanding of footprinting, reconnaissance and 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 security engineer is concerned about DNS zone transfer attacks. Which of the following countermeasures would be MOST effective in preventing unauthorized zone transfers?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Restrict zone transfers to authorized IP addresses only
Restricting zone transfers to authorized IP addresses only is the most effective countermeasure because it directly controls which DNS servers are allowed to request a full copy of the zone data. By configuring an allow-transfer list (e.g., using the 'allow-transfer { trusted_servers; };' directive in BIND), the primary DNS server will reject zone transfer requests from any unauthorized IP, preventing attackers from enumerating all DNS 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.
✓
Restrict zone transfers to authorized IP addresses only
Why this is correct
This limits zone transfer requests to trusted secondary servers, preventing unauthorized parties from obtaining the zone data.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use DNSSEC to sign the zone
Why it's wrong here
DNSSEC provides data integrity and authentication but does not prevent zone transfers; it only protects against DNS spoofing.
✗
Change the default port of 53 to a non-standard port
Why it's wrong here
Changing the port is not a standard practice and can be easily discovered through port scanning. It is not a reliable security measure.
✗
Disable DNS recursion on the server
Why it's wrong here
Disabling recursion prevents the server from resolving queries for external domains, but does not directly prevent zone transfers.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse DNSSEC (which protects data integrity) with access control mechanisms, or they mistakenly think disabling recursion or changing ports will prevent zone transfers, when in fact zone transfers are controlled by explicit authorization settings on the authoritative server.
Detailed technical explanation
How to think about this question
Zone transfers use TCP port 53 (as opposed to UDP for standard queries) and are initiated with an AXFR (full zone transfer) or IXFR (incremental) query. The primary DNS server's allow-transfer list is typically defined per zone in configuration files (e.g., named.conf), and can also be combined with TSIG (Transaction Signatures) for cryptographic authentication of the requesting server. In real-world scenarios, misconfigured DNS servers that allow unrestricted zone transfers are a common source of information leakage during reconnaissance, as tools like 'dig axfr @target zone.name' can dump all records.
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 practitioner preparing for the CEH exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Footprinting, Reconnaissance and Scanning — This question tests Footprinting, Reconnaissance and Scanning — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Restrict zone transfers to authorized IP addresses only — Restricting zone transfers to authorized IP addresses only is the most effective countermeasure because it directly controls which DNS servers are allowed to request a full copy of the zone data. By configuring an allow-transfer list (e.g., using the 'allow-transfer { trusted_servers; };' directive in BIND), the primary DNS server will reject zone transfer requests from any unauthorized IP, preventing attackers from enumerating all DNS records.
What should I do if I get this CEH 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
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which THREE of the following are correct statements about DNS zone transfers?
hard
✓ A.A successful zone transfer reveals all DNS records for the domain
✓ B.The tool dnsrecon can attempt a zone transfer
C.Zone transfers are encrypted by default
✓ D.Zone transfers should be restricted to authorized secondary DNS servers
E.Zone transfers use UDP port 53
Why A: A successful DNS zone transfer (AXFR) returns the complete zone file, which contains all DNS records for the domain, including A, AAAA, MX, CNAME, NS, and TXT records. This is why it is a critical information-gathering step during reconnaissance.
Last reviewed: Jun 24, 2026
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