- A
DNS cache poisoning
Why wrong: Cache poising corrupts DNS records, not generates random queries.
- B
DNS amplification attack
Why wrong: Amplification uses spoofed source IPs to amplify traffic, not random subdomains.
- C
DNS tunneling
Why wrong: DNS tunneling encodes data in DNS queries, but usually uses fewer, longer queries.
- D
Domain generation algorithm (DGA) activity
DGA malware generates many random subdomains to bypass domain blacklists.
Question 607 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 captures traffic and sees a high number of DNS queries for random subdomains under a single domain, all returning NXDOMAIN. This pattern is typical of which malicious activity?
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
✓
Domain generation algorithm (DGA) activity
D is correct because a high volume of DNS queries for random subdomains under a single domain, all returning NXDOMAIN, is a classic indicator of Domain Generation Algorithm (DGA) activity. Malware uses DGA to generate thousands of pseudo-random domain names to contact a command-and-control (C2) server; the NXDOMAIN responses indicate that the generated domains are not yet registered or have been sinkholed.
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 poising corrupts DNS records, not generates random queries.
- ✗
DNS amplification attack
Why it's wrong here
Amplification uses spoofed source IPs to amplify traffic, not random subdomains.
- ✗
DNS tunneling
Why it's wrong here
DNS tunneling encodes data in DNS queries, but usually uses fewer, longer queries.
- ✓
Domain generation algorithm (DGA) activity
Why this is correct
DGA malware generates many random subdomains to bypass domain blacklists.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between DGA activity and DNS tunneling by emphasizing that DGA generates random, unresolvable subdomains (NXDOMAIN), while tunneling uses structured subdomains that typically receive valid responses (e.g., TXT records) to exfiltrate data.
Detailed technical explanation
How to think about this question
DGA malware often implements algorithms based on date, seed, or TLD lists (e.g., Conficker used a seed based on the current date) to generate thousands of domains per day; the NXDOMAIN responses are expected until the C2 server registers a specific domain. Security teams can detect DGA by analyzing NXDOMAIN rates, entropy of query names, and time-based patterns, often using machine learning models to distinguish from legitimate DNS failures. In real-world scenarios, a sudden spike in NXDOMAIN responses for a single domain with high-entropy subdomains (e.g., 'a3f8k2.example.com') is a strong indicator of DGA-based C2 communication.
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.
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?
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: Domain generation algorithm (DGA) activity — D is correct because a high volume of DNS queries for random subdomains under a single domain, all returning NXDOMAIN, is a classic indicator of Domain Generation Algorithm (DGA) activity. Malware uses DGA to generate thousands of pseudo-random domain names to contact a command-and-control (C2) server; the NXDOMAIN responses indicate that the generated domains are not yet registered or have been sinkholed.
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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