Quick Answer
The answer is DNS tunneling. This technique is correct because the attacker encodes stolen data into the subdomain labels of DNS queries sent to a domain they control, allowing them to bypass firewalls and proxies that rarely inspect DNS traffic deeply. On the Certified Ethical Hacker CEH exam, this scenario tests your understanding of covert channels and data exfiltration methods, often appearing in questions about anomalous DNS patterns or unusual query volumes to unknown domains. A common trap is confusing this with DNS poisoning or amplification attacks, but remember: DNS tunneling focuses on data extraction, not cache corruption or bandwidth exhaustion. A helpful memory tip is to think of DNS as a “digital postman”—if the postman is carrying secret messages in the address labels, that’s tunneling.
This CEH practice question tests your understanding of footprinting, reconnaissance and scanning. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
You are investigating a suspected data exfiltration. Network logs show an internal host performing numerous DNS queries to a domain that does not exist in any organization records. The queries use various subdomains. Which technique is the attacker MOST likely using?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
DNS amplification attack
Why wrong: DNS amplification is a DDoS technique.
DNS cache poisoning
Why wrong: DNS cache poising injects false records, not exfiltration.
DNS zone transfer
Why wrong: Zone transfer copies DNS records, not exfiltration.
DNS tunneling
DNS tunneling uses DNS queries to exfiltrate data.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
DNS tunneling
The attacker is most likely using DNS tunneling, which encodes data from exfiltrated information into DNS queries and responses. By making numerous DNS queries to a domain they control, with data encoded in the subdomain labels, the attacker can bypass network security controls that do not inspect DNS traffic deeply. The fact that the domain does not exist in organization records and uses various subdomains is a classic indicator of DNS tunneling.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
DNS amplification attack
Why it's wrong here
DNS amplification is a DDoS technique.
DNS cache poisoning
Why it's wrong here
DNS cache poising injects false records, not exfiltration.
DNS zone transfer
Why it's wrong here
Zone transfer copies DNS records, not exfiltration.
DNS tunneling
Why this is correct
DNS tunneling uses DNS queries to exfiltrate data.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates confuse DNS tunneling with DNS amplification attacks because both involve many DNS queries, but amplification is a DDoS technique focused on volume, not covert data exfiltration via subdomain encoding.
Detailed technical explanation
DNS tunneling works by encoding arbitrary data into DNS query labels (e.g., base32 or base64 encoded chunks) and sending them to a malicious authoritative server. The server can then extract the data from the query names and respond with encoded commands or acknowledgments in the DNS response. Real-world tools like dnscat2 or Iodine implement this by using the full 255-byte limit of a fully qualified domain name and can even tunnel interactive shells over DNS.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Footprinting, Reconnaissance and Scanning — This question tests Footprinting, Reconnaissance and Scanning — Read the scenario before looking for a memorised answer..
The correct answer is: DNS tunneling — The attacker is most likely using DNS tunneling, which encodes data from exfiltrated information into DNS queries and responses. By making numerous DNS queries to a domain they control, with data encoded in the subdomain labels, the attacker can bypass network security controls that do not inspect DNS traffic deeply. The fact that the domain does not exist in organization records and uses various subdomains is a classic indicator of DNS tunneling.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This CEH practice question is part of Courseiva's free EC-Council 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 CEH exam.
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