- A
DNS cache poisoning
Why wrong: Cache poisoning corrupts resolver caches.
- B
DNS amplification
Why wrong: Amplification uses large responses, not many queries.
- C
DNS tunneling
DNS tunneling uses subdomains to encode data.
- D
DNS zone transfer
Why wrong: Zone transfer copies DNS records.
Question 16 of 1,000
200-201 Security Monitoring Practice Question
This 200-201 practice question tests your understanding of security monitoring. 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.
An analyst is investigating a potential data exfiltration via DNS. In Zeek DNS logs, the analyst sees many queries for subdomains like 'a1b2c3.malicious.com', 'd4e5f6.malicious.com' etc. from an internal host. Which technique is likely being used?
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
The repeated pattern of unique, seemingly random subdomains (e.g., 'a1b2c3.malicious.com') from a single internal host is a classic indicator of DNS tunneling. This technique encodes exfiltrated data into DNS query subdomains, leveraging the fact that DNS traffic is often allowed through firewalls. The malicious server decodes the subdomain strings to reconstruct the stolen data.
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 cache poisoning
Why it's wrong here
Cache poisoning corrupts resolver caches.
- ✗
DNS amplification
Why it's wrong here
Amplification uses large responses, not many queries.
- ✓
DNS tunneling
Why this is correct
DNS tunneling uses subdomains to encode data.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
DNS zone transfer
Why it's wrong here
Zone transfer copies DNS records.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between DNS tunneling (data exfiltration) and DNS amplification (DDoS), where candidates mistakenly associate any unusual DNS pattern with a volumetric attack rather than a covert channel.
Detailed technical explanation
How to think about this question
DNS tunneling works by encoding payload data (e.g., base64-encoded chunks) into the subdomain labels of DNS queries, which are then sent to an attacker-controlled authoritative nameserver. The server logs the queries and decodes the data, while responses can carry commands or acknowledgments. This technique exploits the fact that DNS queries are typically small (UDP, <512 bytes) and often pass through security controls unchecked, though modern solutions like DNS firewalls or response-policy zones (RPZ) can detect high-frequency, entropy-rich subdomain patterns.
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
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FAQ
Questions learners often ask
What does this 200-201 question test?
Security Monitoring — This question tests Security Monitoring — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: DNS tunneling — The repeated pattern of unique, seemingly random subdomains (e.g., 'a1b2c3.malicious.com') from a single internal host is a classic indicator of DNS tunneling. This technique encodes exfiltrated data into DNS query subdomains, leveraging the fact that DNS traffic is often allowed through firewalls. The malicious server decodes the subdomain strings to reconstruct the stolen data.
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.
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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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