200-201 Network Intrusion Analysis Practice Question
A network analyst finds a PCAP with a series of DNS queries for subdomains like "data12345.example.com" and "data67890.example.com" where the subdomain names appear to contain encoded base64 data. This pattern suggests:
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 exfiltration
DNS exfiltration encodes data in subdomain names to bypass security controls, as DNS is often allowed through firewalls.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Port scan via DNS
Why it's wrong here
Port scanning is not done via DNS subdomains.
- ✗
Normal DNS resolution
Why it's wrong here
Normal DNS queries do not have base64-encoded subdomains.
- ✗
DGA-based C2
Why it's wrong here
DGA domains are random-looking, but not necessarily carrying encoded data in subdomains.
- ✓
DNS tunnelling for exfiltration
Why this is correct
Encoding data in subdomains for exfiltration is DNS tunnelling.
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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.