- A
Replay attack using previously captured packets
Why wrong: Replay attacks resend previously valid traffic to trick a system into accepting an old authentication or transaction. They do not normally produce a large burst of unrelated DNS responses from third-party resolvers.
- B
DNS reflection and amplification denial-of-service attack
This is the best match. The attacker sends small DNS requests that cause open resolvers to send much larger responses to the victim's IP address. Because the victim receives the responses, the attack uses reflection; because the responses are much larger than the requests, it also uses amplification. The result is bandwidth exhaustion and severe latency, which are common symptoms of a volumetric DDoS attack.
- C
ARP poisoning that redirects local traffic on a LAN
Why wrong: ARP poisoning affects Layer 2 traffic within a local broadcast domain, usually to intercept or redirect traffic on the same LAN. It does not explain Internet-scale DNS responses arriving from many open resolvers.
- D
Session hijacking through stolen authentication cookies
Why wrong: Session hijacking focuses on taking over an authenticated user session. It does not create a pattern of small outbound DNS queries followed by a much larger inbound flood of DNS responses from third-party servers.
SY0-701 Threats, Vulnerabilities, and Mitigations Practice Question
This SY0-701 practice question tests your understanding of threats, vulnerabilities, and mitigations. 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 web service begins experiencing severe latency. Netflow shows thousands of short DNS queries leaving the attacker network, while a much larger volume of DNS responses is arriving at the victim’s public IP address from many open resolvers. Which attack is most likely occurring?
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 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
DNS reflection and amplification denial-of-service attack
The attack described is a DNS reflection and amplification denial-of-service attack. The attacker sends thousands of short DNS queries with a spoofed source IP (the victim's IP) to many open resolvers, which then send large DNS responses to the victim, overwhelming its bandwidth. NetFlow shows a small volume of queries leaving the attacker and a much larger volume of responses arriving at the victim, which is the hallmark of amplification (small request, large response) combined with reflection (responses from third-party resolvers).
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.
- ✗
Replay attack using previously captured packets
Why it's wrong here
Replay attacks resend previously valid traffic to trick a system into accepting an old authentication or transaction. They do not normally produce a large burst of unrelated DNS responses from third-party resolvers.
- ✓
DNS reflection and amplification denial-of-service attack
Why this is correct
This is the best match. The attacker sends small DNS requests that cause open resolvers to send much larger responses to the victim's IP address. Because the victim receives the responses, the attack uses reflection; because the responses are much larger than the requests, it also uses amplification. The result is bandwidth exhaustion and severe latency, which are common symptoms of a volumetric DDoS attack.
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.
- ✗
ARP poisoning that redirects local traffic on a LAN
Why it's wrong here
ARP poisoning affects Layer 2 traffic within a local broadcast domain, usually to intercept or redirect traffic on the same LAN. It does not explain Internet-scale DNS responses arriving from many open resolvers.
- ✗
Session hijacking through stolen authentication cookies
Why it's wrong here
Session hijacking focuses on taking over an authenticated user session. It does not create a pattern of small outbound DNS queries followed by a much larger inbound flood of DNS responses from third-party servers.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse the high volume of responses arriving at the victim with a simple volumetric attack, missing the key indicators of reflection (responses from many different IPs) and amplification (small queries generating large responses), which uniquely identify a DNS reflection/amplification DDoS.
Detailed technical explanation
How to think about this question
DNS reflection attacks exploit the fact that a small DNS query (e.g., 60 bytes for an ANY query) can elicit a much larger response (e.g., over 4000 bytes with DNSSEC records), providing an amplification factor of up to 70x. Attackers use botnets to send these queries with the victim's spoofed IP to thousands of open resolvers, which are misconfigured to respond to any query from any source. Mitigation includes disabling open recursion on resolvers, implementing BCP 38 (source IP validation), and using rate limiting or response-size filtering.
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 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.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this SY0-701 question test?
Threats, Vulnerabilities, and Mitigations — This question tests Threats, Vulnerabilities, and Mitigations — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: DNS reflection and amplification denial-of-service attack — The attack described is a DNS reflection and amplification denial-of-service attack. The attacker sends thousands of short DNS queries with a spoofed source IP (the victim's IP) to many open resolvers, which then send large DNS responses to the victim, overwhelming its bandwidth. NetFlow shows a small volume of queries leaving the attacker and a much larger volume of responses arriving at the victim, which is the hallmark of amplification (small request, large response) combined with reflection (responses from third-party resolvers).
What should I do if I get this SY0-701 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
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Last reviewed: Jun 11, 2026
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