- A
An SIEM alert for any DNS query exceeding 100 bytes
Why wrong: Although DNS tunneling may have larger payloads, this could generate false positives and does not specifically detect tunneling.
- B
A Snort rule blocking traffic to known malicious IPs
Why wrong: This is too static and does not cover DNS tunneling, which uses legitimate DNS infrastructure.
- C
A firewall rule that blocks all DNS requests from internal servers
Why wrong: This would disrupt legitimate DNS traffic and is not a precise detection method.
- D
A YARA rule that flags DNS queries with high entropy domain names
High entropy in domain names is a common indicator of DNS tunneling.
Question 379 of 1,000
CS0-003 Incident Response and Management Practice Question
This CS0-003 practice question tests your understanding of incident response and management. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
After containing a data breach, the incident response team discovers that an attacker exfiltrated sensitive data over DNS tunneling. Which of the following detection rules would BEST identify similar activity in the future?
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
✓
A YARA rule that flags DNS queries with high entropy domain names
DNS tunneling often involves unusual domain names with high entropy or long subdomains. A YARA rule targeting DNS query patterns can detect such anomalies.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
An SIEM alert for any DNS query exceeding 100 bytes
Why it's wrong here
Although DNS tunneling may have larger payloads, this could generate false positives and does not specifically detect tunneling.
- ✗
A Snort rule blocking traffic to known malicious IPs
Why it's wrong here
This is too static and does not cover DNS tunneling, which uses legitimate DNS infrastructure.
- ✗
A firewall rule that blocks all DNS requests from internal servers
Why it's wrong here
This would disrupt legitimate DNS traffic and is not a precise detection method.
- ✓
A YARA rule that flags DNS queries with high entropy domain names
Why this is correct
High entropy in domain names is a common indicator of DNS tunneling.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A SOC analyst notices unusual lateral movement in the network at 2 AM. The IR playbook dictates: identify and contain (isolate the affected machine), then eradicate (remove the malware), then recover (restore from backup), then document. Skipping containment before eradication risks the attacker regaining access. Questions like this test the sequence and rationale of incident response phases.
Visual reference
What to study next
Got this wrong? Here's your next step.
Identify which CS0-003 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Questions learners often ask
What does this CS0-003 question test?
Incident Response and Management — This question tests Incident Response and Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A YARA rule that flags DNS queries with high entropy domain names — DNS tunneling often involves unusual domain names with high entropy or long subdomains. A YARA rule targeting DNS query patterns can detect such anomalies.
What should I do if I get this CS0-003 question wrong?
Identify which CS0-003 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
This CS0-003 practice question is part of Courseiva's free CompTIA 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 CS0-003 exam.
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