The answer is that the host is the victim of a DNS amplification attack. This conclusion follows because the internal host, which is not a DNS server, is seen in the NetFlow data sending small UDP packets to many external IPs on port 53—this is the attacker spoofing the victim’s source address to trigger open DNS resolvers, which then flood the victim with large responses. On the Cisco CyberOps Associate 200-201 exam, this scenario tests your ability to interpret NetFlow records for anomaly detection, specifically distinguishing between a host initiating queries and one receiving reflected traffic. A common trap is misreading the flow direction: the small outbound packets are the spoofed queries, not the attack itself. Remember the memory tip “small out, big in” to spot DNS amplification in NetFlow analysis.
200-201 Network Intrusion Analysis Practice Question
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.
An analyst reviews NetFlow data and sees a single internal IP communicating with many external IPs on port 53, each with small UDP packets. The internal host is not a DNS server. What is the most likely explanation?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The host is the victim of a DNS amplification attack
The internal host is not a DNS server, yet it is sending small UDP packets to many external IPs on port 53. This is characteristic of a DNS amplification attack, where the attacker spoofs the victim's IP address and sends small queries to open DNS resolvers, which then send large responses to the victim. The NetFlow data shows the victim receiving the amplified traffic, not initiating it, making C correct.
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.
The host is the victim of a DNS amplification attack
Why this is correct
The host's IP is spoofed as the source of queries to many open resolvers, causing replies to flood the host.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The host is scanning for open DNS resolvers
Why it's wrong here
Scanning would show responses from many IPs, not requests from the host to many IPs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between the victim and the attacker in amplification attacks; the trap here is that candidates see many small UDP packets and assume the host is initiating queries (e.g., scanning or DNS lookups), rather than recognizing that the host is the victim receiving the amplified responses.
Trap categories for this question
Command / output trap
Scanning would show responses from many IPs, not requests from the host to many IPs.
Detailed technical explanation
How to think about this question
In a DNS amplification attack, the attacker sends small DNS queries (e.g., type ANY or TXT) with a spoofed source IP (the victim's) to open resolvers, which respond with large payloads (up to 4096 bytes via EDNS0). This creates a traffic amplification factor of 50-100x, overwhelming the victim. NetFlow records show the victim's IP as the destination with many small incoming UDP packets on port 53, but the actual attack traffic is the large responses from resolvers, which may be fragmented or truncated in flow records.
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.
TExam Day Tips
→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 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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Intrusion Analysis — This question tests Network Intrusion Analysis — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The host is the victim of a DNS amplification attack — The internal host is not a DNS server, yet it is sending small UDP packets to many external IPs on port 53. This is characteristic of a DNS amplification attack, where the attacker spoofs the victim's IP address and sends small queries to open DNS resolvers, which then send large responses to the victim. The NetFlow data shows the victim receiving the amplified traffic, not initiating it, making C correct.
What should I do if I get this 200-201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
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 →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.