Quick Answer
The answer is DNS log analysis because DNS tunneling detection relies on identifying the abnormal patterns that malware creates when it encodes stolen data within DNS queries and responses. This technique exploits the trust placed in DNS traffic, often using TXT or A records to hide exfiltrated data, but it leaves forensic traces that only log analysis can reliably reveal—such as unusually long domain names, a spike in NXDOMAIN responses, or excessive queries to a single external server. On the Cisco CyberOps Associate 200-201 exam, this question tests your understanding of how to apply different analysis methods to specific attack vectors; a common trap is to choose packet-level inspection or flow analysis, but those lack the contextual record of DNS transactions needed to spot tunneling. Remember the memory tip: “DNS logs don’t lie—long names and NXDOMAINs are the telltale signs of a tunnel.”
This 200-201 practice question tests your understanding of network intrusion analysis. 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.
A host is infected with malware that uses DNS tunneling to exfiltrate data. Which type of analysis would best detect this activity?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
DNS log analysis
DNS logs show query names, sizes, and frequency.
Windows event log analysis
Why wrong: Windows logs do not capture DNS queries natively.
Firewall log analysis
Why wrong: Firewall logs show connections but not DNS query details.
NetFlow analysis
Why wrong: NetFlow shows flow data, not DNS queries.
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 log analysis
DNS tunneling encodes exfiltrated data within DNS queries or responses, often using TXT or A record types to bypass network security controls. DNS log analysis is the most direct detection method because it reveals anomalous patterns such as unusually long domain names, excessive NXDOMAIN responses, or high volumes of DNS traffic to a single external server, which are hallmarks of tunneling activity.
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 log analysis
Why this is correct
DNS logs show query names, sizes, and frequency.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Windows event log analysis
Why it's wrong here
Windows logs do not capture DNS queries natively.
Firewall log analysis
NetFlow analysis
Why it's wrong here
NetFlow shows flow data, not DNS queries.
Common exam traps
Cisco often tests the misconception that firewall logs or NetFlow are sufficient for detecting application-layer tunneling, when in fact only DNS-specific logs provide the granularity to see the encoded payloads within DNS queries.
Trap categories for this question
Command / output trap
Firewall logs show connections but not DNS query details.
Detailed technical explanation
DNS tunneling exploits the fact that DNS traffic is often allowed through firewalls without deep inspection. Tools like dnscat2 or Iodine encode data in subdomain labels (e.g., <base64-encoded-data>.attacker.com), and the authoritative DNS server decodes the responses. Detection relies on analyzing DNS logs for entropy spikes in query names, abnormal query sizes (e.g., >255 bytes for a single label), or a high ratio of TXT queries to other record types.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
Network Intrusion Analysis — This question tests Network Intrusion Analysis — Read the scenario before looking for a memorised answer..
The correct answer is: DNS log analysis — DNS tunneling encodes exfiltrated data within DNS queries or responses, often using TXT or A record types to bypass network security controls. DNS log analysis is the most direct detection method because it reveals anomalous patterns such as unusually long domain names, excessive NXDOMAIN responses, or high volumes of DNS traffic to a single external server, which are hallmarks of tunneling activity.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Read the scenario before looking for a memorised answer.
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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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