200-201 Network Intrusion Analysis Practice Question
An analyst detects traffic from an internal host that periodically sends small DNS queries to a domain with high entropy subdomains (e.g., 'a3k9f2.example.com'). The domain is not on any blocklist, and the query intervals are consistent every 60 seconds. Which technique is most 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 tunnelling for C2 communication
DNS tunnelling encodes data in subdomain queries, and periodic beaconing is common for C2. High entropy subdomains and regular intervals suggest DNS tunnelling for 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 tunnelling for C2 communication
Why this is correct
Encoded data in subdomains with regular intervals is typical of DNS tunnelling for command and control.
- ✗
DNS amplification attack
Why it's wrong here
DNS amplification involves spoofed source IP to amplify traffic, not periodic queries.
- ✗
Normal DNS resolution for a dynamic DNS service
Why it's wrong here
Dynamic DNS may have low entropy subdomains, not high entropy, and intervals may vary.
- ✗
DNS cache poisoning attempt
Why it's wrong here
Cache poisoning involves corrupting DNS records, not periodic queries.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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