The answer is a DNS amplification DDoS attack. This is correct because the attacker spoofs the victim’s IP address in small DNS queries sent to open resolvers, which then respond with much larger DNS replies, flooding the victim’s bandwidth—a classic amplification effect that exploits UDP’s stateless nature. On the Security+ SY0-701 exam, this scenario tests your ability to recognize amplification attacks by their signature imbalance: small requests generating massive responses from many sources. A common trap is confusing this with a reflected attack, but the key distinction is the size multiplier—amplification relies on the response being significantly larger than the query. For a quick memory tip, think “small query, big reply, victim’s IP is the lie”—the spoofed source IP is the attacker’s trick to redirect the flood.
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 public-facing web service suddenly becomes very slow. NetFlow shows a high volume of small DNS queries leaving attacker-controlled systems and much larger DNS responses arriving at the victim's IP address from many different resolvers. Which attack is taking place?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
DNS amplification DDoS
This is a DNS amplification DDoS attack. The attacker sends small DNS queries with a spoofed source IP (the victim's IP) to open DNS resolvers, which then send large DNS responses to the victim. The high volume of small queries and much larger responses from many resolvers is the classic signature of an amplification attack, exploiting the UDP protocol's lack of source verification.
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.
✓
DNS amplification DDoS
Why this is correct
DNS amplification uses small spoofed queries to elicit much larger responses toward the victim.
Related concept
Read the scenario before looking for a memorised answer.
✗
Replay attack
Why it's wrong here
A replay attack reuses captured valid traffic, which does not explain the response-heavy flood pattern.
✗
ARP poisoning
Why it's wrong here
ARP poisoning affects local network address resolution and would not generate distributed DNS responses.
✗
Session fixation
Why it's wrong here
Session fixation manipulates a web session identifier, not bandwidth through reflective DNS traffic.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may confuse the high volume of DNS traffic with a normal DNS flood or a reflection attack, but the key differentiator is the amplification ratio—small queries generating large responses—which is unique to amplification DDoS, not a simple reflection or volumetric flood.
Detailed technical explanation
How to think about this question
DNS amplification exploits the fact that a small DNS query (e.g., 60 bytes for an ANY record) can trigger a response up to 4000 bytes, giving an amplification factor of ~70x. Attackers often use botnets to send these queries to thousands of open resolvers, and the victim's IP is flooded with unsolicited responses, saturating bandwidth. Real-world examples include the 2016 Dyn DDoS attack, which used DNS amplification among other vectors.
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 security team runs a vulnerability scan on a web application and discovers an unpatched SQL injection flaw. The team prioritises remediation by CVSS score — critical flaws are patched within 24 hours, high within 7 days. Questions like this test whether you understand vulnerability management processes, scanning tools, and remediation prioritisation.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this SY0-701 question in full detail.
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 amplification DDoS — This is a DNS amplification DDoS attack. The attacker sends small DNS queries with a spoofed source IP (the victim's IP) to open DNS resolvers, which then send large DNS responses to the victim. The high volume of small queries and much larger responses from many resolvers is the classic signature of an amplification attack, exploiting the UDP protocol's lack of source verification.
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.
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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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 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?
medium
A.Replay attack using previously captured packets
✓ B.DNS reflection and amplification denial-of-service attack
C.ARP poisoning that redirects local traffic on a LAN
D.Session hijacking through stolen authentication cookies
Why B: 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).
Last reviewed: Jun 11, 2026
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