- A
DNS queries with long subdomain strings
Correct. Long subdomain strings are a sign of DNS tunneling.
- B
Frequent DNS queries to known domains
Why wrong: Frequent queries to known domains are normal.
- C
DNS responses with large payloads
Why wrong: Large responses are more associated with amplification attacks.
- D
DNS queries using TCP instead of UDP
Why wrong: DNS over TCP is used for zone transfers or large responses, not necessarily tunneling.
Question 15 of 1,000
200-201 Network Intrusion Analysis Practice Question
This 200-201 practice question tests your understanding of network intrusion analysis. 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.
Which of the following is a common indicator of DNS tunneling used for exfiltration?
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 queries with long subdomain strings
DNS tunneling exploits the DNS protocol to encapsulate non-DNS data within DNS queries and responses. A common indicator is DNS queries with unusually long subdomain strings, as attackers encode exfiltrated data into the query name to bypass network security controls.
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 queries with long subdomain strings
Why this is correct
Correct. Long subdomain strings are a sign of DNS tunneling.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Frequent DNS queries to known domains
Why it's wrong here
Frequent queries to known domains are normal.
- ✗
DNS responses with large payloads
Why it's wrong here
Large responses are more associated with amplification attacks.
- ✗
DNS queries using TCP instead of UDP
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between a general anomaly (like large DNS responses) and a specific tunneling indicator (long subdomain strings), where candidates mistakenly focus on response size or protocol choice rather than the query structure.
Detailed technical explanation
How to think about this question
In DNS tunneling, the attacker registers a domain and sets up a malicious DNS server. The compromised client sends DNS queries with subdomains containing base64-encoded or otherwise obfuscated data (e.g., 'exfil-data.attacker.com'). The server's response can include commands or acknowledgments, making the channel bidirectional. Tools like dnscat2 and Iodine automate this process, often using TXT or NULL record types to maximize payload capacity.
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 200-201 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.
Visual reference
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 200-201 question test?
Network Intrusion Analysis — This question tests Network Intrusion Analysis — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: DNS queries with long subdomain strings — DNS tunneling exploits the DNS protocol to encapsulate non-DNS data within DNS queries and responses. A common indicator is DNS queries with unusually long subdomain strings, as attackers encode exfiltrated data into the query name to bypass network security controls.
What should I do if I get this 200-201 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
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Last reviewed: Jul 4, 2026
This 200-201 practice question is part of Courseiva's free Cisco 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 200-201 exam.
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