200-201 Security Monitoring Practice Question
A SOC analyst observes a spike in DNS queries for long, random-looking subdomains under a single domain from an internal host. The responses are NXDOMAIN. Which type of activity is most likely indicated?
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
Random subdomain queries with NXDOMAIN responses are typical of a DNS tunneling attempt used for data exfiltration or C2.
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
Amplification uses open resolvers with spoofed source IPs, not random subdomains.
- ✓
DNS tunneling
Why this is correct
Random subdomains encoding data is a hallmark of DNS tunneling.
- ✗
Normal DNS resolution for many websites
Why it's wrong here
Normal DNS would not have random subdomains.
- ✗
Misconfigured DNS server
Why it's wrong here
Misconfiguration might cause NXDOMAIN but not random subdomains.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.