212-89 Network Incidents Practice Question
You suspect a DNS tunneling attack for data exfiltration. In your DNS server logs, which characteristic is the strongest indicator of a tunnel rather than standard recursive lookups?
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
✓
Unusually long, high-entropy subdomains
DNS tunneling often uses non-standard, long, or high-entropy subdomains to encode 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.
- ✗
High volume of A records
Why it's wrong here
A high volume of A records could just mean a busy web server.
- ✗
Requests for PTR records
Why it's wrong here
PTR records are standard for reverse lookups.
- ✓
Unusually long, high-entropy subdomains
Why this is correct
High-entropy strings are a hallmark of encoded data within DNS queries.
- ✗
Queries to root hints
Why it's wrong here
Requests to root hints are normal behavior for recursive DNS servers.
Visual reference
About these practice questions
Courseiva writes every 212-89 question from scratch — 206 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official EC-Council exam blueprint
This 212-89 practice question is part of Courseiva's free EC-Council 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 212-89 exam.