- A
DNS amplification attack
Why wrong: DNS amplification is a DDoS technique where an attacker sends small queries with spoofed IPs to generate large responses; here the server is sending queries to an external IP, and it's sending queries, not receiving them with spoofed source.
- B
DNS tunneling
DNS tunneling uses DNS protocol to encapsulate other data, often for command-and-control or data exfiltration. Large response sizes and unusual use of TCP port 53 are indicators.
- C
DNS zone transfer
Why wrong: A zone transfer is a legitimate DNS replication mechanism between authoritative servers; it uses TCP port 53 but is not used for data exfiltration from a non-DNS server.
- D
DNS cache poisoning
Why wrong: DNS cache poising involves inserting false records into a DNS resolver's cache; it does not involve a server sending many queries or large responses for exfiltration.
N10-009 Network Security Practice Question
This N10-009 practice question tests your understanding of network security. 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 analyst is investigating a potential data exfiltration. The analyst notices that a server is sending DNS queries to an external IP address on TCP port 53, and the DNS responses are unusually large. The server is not a DNS server. Which technique is most likely being used?
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.
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
DNS tunneling
DNS tunneling encodes non-DNS data (e.g., exfiltrated files) within DNS queries and responses, often using TCP port 53 to bypass firewalls. The unusually large responses are a hallmark of tunneled data being returned in DNS payloads, and the fact that the server is not a DNS server strongly indicates it is being used as a client for covert data transfer.
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 amplification attack
Why it's wrong here
DNS amplification is a DDoS technique where an attacker sends small queries with spoofed IPs to generate large responses; here the server is sending queries to an external IP, and it's sending queries, not receiving them with spoofed source.
When this WOULD be correct
A DNS amplification attack would be correct if the question described a server sending small DNS queries to open resolvers with a spoofed source IP (the victim), resulting in large responses flooding the victim.
- ✓
DNS tunneling
Why this is correct
DNS tunneling uses DNS protocol to encapsulate other data, often for command-and-control or data exfiltration. Large response sizes and unusual use of TCP port 53 are indicators.
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.
- ✗
DNS zone transfer
- ✗
DNS cache poisoning
Why it's wrong here
DNS cache poising involves inserting false records into a DNS resolver's cache; it does not involve a server sending many queries or large responses for exfiltration.
When this WOULD be correct
A question describing a user being redirected to a malicious site after a DNS resolver returns incorrect IP addresses, with no mention of data exfiltration or large responses, would make DNS cache poisoning correct.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The N10-009 exam frequently reuses these exact scenarios with slightly different constraints.
✓DNS tunnelingCorrect answer▾
Why this is correct
DNS tunneling uses DNS protocol to encapsulate other data, often for command-and-control or data exfiltration. Large response sizes and unusual use of TCP port 53 are indicators.
✗DNS amplification attackWrong answer — click to see why▾
Why this is wrong here
A DNS amplification attack uses UDP, not TCP, and involves sending small queries that generate large responses to a victim, not to an external IP from a server. The server here is the source, not the target.
★ When this WOULD be the correct answer
A DNS amplification attack would be correct if the question described a server sending small DNS queries to open resolvers with a spoofed source IP (the victim), resulting in large responses flooding the victim.
Why candidates choose this
Candidates may confuse 'unusually large DNS responses' with amplification, but they overlook the TCP port 53 and the server initiating queries to an external IP, which points to tunneling instead.
✗DNS zone transferWrong answer — click to see why▾
Why this is wrong here
DNS zone transfer is used to replicate DNS databases between authoritative servers, not for data exfiltration. The scenario involves a non-DNS server sending queries to an external IP, which is characteristic of tunneling, not zone transfer.
★ When this WOULD be the correct answer
A question describing a secondary DNS server failing to synchronize with a primary server, with large zone data transfers occurring over TCP port 53, would make DNS zone transfer the correct answer.
Why candidates choose this
Candidates may confuse large DNS responses with zone transfers, or think that any unusual DNS traffic on TCP port 53 indicates a zone transfer, overlooking the data exfiltration context.
✗DNS cache poisoningWrong answer — click to see why▾
Why this is wrong here
DNS cache poisoning involves corrupting a DNS resolver's cache with false records, not exfiltrating data via large DNS responses. The scenario describes data exfiltration, not cache manipulation.
★ When this WOULD be the correct answer
A question describing a user being redirected to a malicious site after a DNS resolver returns incorrect IP addresses, with no mention of data exfiltration or large responses, would make DNS cache poisoning correct.
Why candidates choose this
Candidates may confuse DNS cache poisoning with DNS tunneling because both involve DNS abuse, but cache poisoning focuses on redirection, not data exfiltration via response size.
Analysis generated from the official N10-009blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between DNS amplification (a DDoS attack using UDP reflection) and DNS tunneling (a covert channel using TCP or UDP for data exfiltration), and the trap here is that candidates see 'large responses' and immediately think amplification, ignoring the TCP port 53 and non-DNS server context.
Detailed technical explanation
How to think about this question
DNS tunneling exploits the fact that DNS messages can carry up to 512 bytes in UDP (or up to 65,535 bytes over TCP via EDNS0). Tools like dnscat2 or Iodine encode data in subdomains or TXT records, and the server's response can carry exfiltrated data in the answer section. Real-world detection often involves monitoring for high volumes of TXT queries, abnormal domain lengths, or non-standard TTL values.
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 N10-009 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
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this N10-009 question test?
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: DNS tunneling — DNS tunneling encodes non-DNS data (e.g., exfiltrated files) within DNS queries and responses, often using TCP port 53 to bypass firewalls. The unusually large responses are a hallmark of tunneled data being returned in DNS payloads, and the fact that the server is not a DNS server strongly indicates it is being used as a client for covert data transfer.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 30, 2026
This N10-009 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 N10-009 exam.
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