hardMultiple Choice
200-201 Practice Question: An analyst is investigating a potential data…
An analyst is investigating a potential data exfiltration. The logs show a series of DNS queries with subdomains that appear to be base64-encoded strings. Which technique is likely being used?
⚠ Common exam trap
Cisco often tests the distinction between DNS tunneling (data exfiltration via subdomain encoding) and DNS amplification (a volumetric DDoS attack), so candidates must recognize that base64-encoded subdomains point to tunneling, not amplification.
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
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DNS tunneling
DNS tunneling encodes data (e.g., exfiltrated files) into subdomains of DNS queries, which are then sent to a malicious authoritative DNS server controlled by the attacker. The base64-encoded subdomains in the logs are a classic indicator of this technique, as the attacker uses the DNS protocol to bypass network security controls and covertly transmit data.
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 tunneling
Why this is correct
DNS tunneling encapsulates data in DNS queries to exfiltrate information.
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DNS amplification
Why it's wrong here
DNS amplification is a reflection denial-of-service technique that spoofs source addresses to flood a victim with oversized responses; it moves no data out of the network. It is tempting because it also abuses DNS, but it would be the answer for volumetric DDoS, not for encoded subdomains carrying stolen data.
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Fast flux
Why it's wrong here
Fast flux rapidly rotates the IP addresses returned for a hostname to keep malicious infrastructure alive; the query names themselves stay constant and carry no payload. It is tempting because it also involves DNS abuse, but it would be correct when investigating resilient command-and-control hosting, not encoded exfiltration.
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Domain generation algorithm
Why it's wrong here
A domain generation algorithm produces large volumes of pseudo-random domain names that malware queries for rendezvous; those names are not base64-encoded data. It is tempting because it also generates many DNS queries, but it would be correct when the pattern shows algorithmically generated rendezvous domains, not encoded subdomains.
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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.