Quick Answer
The correct answer is DNS tunneling for data exfiltration. This technique works by encoding stolen data into the subdomain labels of DNS queries—such as randomstring.google.com—where each query carries a small payload of exfiltrated information, allowing attackers to bypass firewalls and proxies that typically permit DNS traffic. On the Cisco CyberOps Associate 200-201 exam, this scenario tests your ability to recognize anomalous DNS patterns as a key indicator of compromise (IoC), often appearing in questions about data exfiltration methods or network-based attacks. A common trap is confusing this with a DDoS amplification attack, but remember that DNS tunneling involves a single internal host generating many unique subdomain queries to a legitimate domain, not a flood of requests to random external servers. For a quick memory tip: think of the subdomain as a “secret envelope” carrying data out through the DNS door.
This 200-201 practice question tests your understanding of security monitoring. 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.
An analyst observes a sudden spike in DNS queries from an internal host to a random subdomain of a legitimate domain (e.g., randomstring.google.com). This behavior is consistent with which technique?
DNS tunneling for data exfiltration.
Uses DNS queries to covertly send data.
HTTP beaconing to a C2 server.
Why wrong: Uses HTTP, not DNS.
DNS amplification attack.
Why wrong: Uses open resolvers to flood victim.
Port scanning using DNS.
Why wrong: DNS not used for port scanning.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
DNS tunneling for data exfiltration.
The sudden spike in DNS queries to random subdomains of a legitimate domain (e.g., randomstring.google.com) is a classic indicator of DNS tunneling. This technique encodes data into DNS query names and exfiltrates it through the DNS protocol, bypassing network security controls that allow DNS traffic.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
DNS tunneling for data exfiltration.
Why this is correct
Uses DNS queries to covertly send data.
Related concept
Read the scenario before looking for a memorised answer.
HTTP beaconing to a C2 server.
DNS amplification attack.
Why it's wrong here
Uses open resolvers to flood victim.
Port scanning using DNS.
Why it's wrong here
DNS not used for port scanning.
Common exam traps
Cisco often tests the distinction between DNS tunneling (data exfiltration) and DNS amplification (DDoS attack), so candidates may confuse the high volume of queries in tunneling with the reflection/amplification mechanism of a DDoS attack.
Detailed technical explanation
DNS tunneling works by encoding data in the subdomain labels of DNS queries, often using base32 or base64, and sending them to a malicious authoritative DNS server controlled by the attacker. The server decodes the queries and can respond with additional data in the TXT or CNAME record responses, enabling bidirectional communication. In real-world scenarios, tools like dnscat2 or Iodine are used, and the high volume of NXDOMAIN responses or unusual query patterns can be detected by monitoring DNS logs.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the 200-201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Security Monitoring — This question tests Security Monitoring — Read the scenario before looking for a memorised answer..
The correct answer is: DNS tunneling for data exfiltration. — The sudden spike in DNS queries to random subdomains of a legitimate domain (e.g., randomstring.google.com) is a classic indicator of DNS tunneling. This technique encodes data into DNS query names and exfiltrates it through the DNS protocol, bypassing network security controls that allow DNS traffic.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A SOC analyst is tuning a correlation rule that detects DNS tunneling. The rule currently generates 500 alerts per day, but only 5% are true positives. Which tuning approach would best reduce false positives while maintaining detection efficacy?
hardWhy D: Option B is correct because adding a threshold for domain query rate per IP reduces noise from normal high-volume DNS activity. Option A is wrong because increasing the time window may increase false positives. Option C is wrong because decreasing entropy threshold may cause more false positives. Option D is wrong because disabling the rule loses detection.
Last reviewed: Jun 11, 2026
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.
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