- A
DNS zone transfer abuse against the organization.
Why wrong: Zone transfer abuse would involve pulling DNS records from an authoritative server, not flooding a victim with amplified responses.
- B
DNS amplification reflection denial-of-service.
This is DNS amplification reflection because the attacker spoofs the victim's IP address in small requests to open resolvers, causing large responses to be sent to the victim instead. The result is a bandwidth flood that can make the server unreachable even though the victim never initiated the traffic. The key clues are tiny queries, spoofed source addresses, many resolvers, and a high volume of unsolicited responses. This is a classic distributed denial-of-service pattern.
- C
A replay attack against a web application session token.
Why wrong: Replay attacks reuse captured credentials or tokens, but they do not produce the resolver-based traffic pattern described in the scenario.
- D
ARP poisoning inside the local network segment.
Why wrong: ARP poisoning is a local Layer 2 attack and would not explain internet-scale DNS responses from external resolvers.
Quick Answer
The answer is a DNS amplification reflection DDoS attack. This is correct because the attacker spoofs the victim’s IP address as the source of tiny DNS queries sent to open resolvers, which then flood the victim with much larger DNS responses—amplifying the traffic by a factor of up to 50 or more. On the Security+ SY0-701 exam, this scenario tests your understanding of how reflection (using the victim’s IP as the source) and amplification (small query, large response) combine to overwhelm bandwidth. A common trap is confusing this with a simple DNS flood or a SYN flood; remember that the key clue is the victim sending only tiny queries while receiving massive replies. Memory tip: think “small ask, big blast” to recall the amplification factor, and “spoofed source, reflected back” for the reflection vector.
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 web server becomes unreachable during an outage. Netflow shows a large number of DNS responses arriving from many open resolvers, while the server itself only sent tiny spoofed DNS queries with the victim's address as the source. What type of attack is this?
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 amplification reflection denial-of-service.
This is a classic DNS amplification reflection DDoS attack. The attacker sends small DNS queries with a spoofed source IP (the victim's address) to open resolvers, which then send large DNS responses to the victim, overwhelming its bandwidth. The NetFlow data shows the server receiving many large DNS responses while only sending tiny spoofed queries, confirming the amplification and reflection vectors.
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 zone transfer abuse against the organization.
Why it's wrong here
Zone transfer abuse would involve pulling DNS records from an authoritative server, not flooding a victim with amplified responses.
- ✓
DNS amplification reflection denial-of-service.
Why this is correct
This is DNS amplification reflection because the attacker spoofs the victim's IP address in small requests to open resolvers, causing large responses to be sent to the victim instead. The result is a bandwidth flood that can make the server unreachable even though the victim never initiated the traffic. The key clues are tiny queries, spoofed source addresses, many resolvers, and a high volume of unsolicited responses. This is a classic distributed denial-of-service pattern.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
A replay attack against a web application session token.
Why it's wrong here
Replay attacks reuse captured credentials or tokens, but they do not produce the resolver-based traffic pattern described in the scenario.
- ✗
ARP poisoning inside the local network segment.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing the direction of traffic: candidates may think the server is the attacker because it sends queries, but the spoofed source IP and large incoming responses reveal it is the victim of a reflection attack.
Trap categories for this question
Scenario analysis trap
Replay attacks reuse captured credentials or tokens, but they do not produce the resolver-based traffic pattern described in the scenario.
Detailed technical explanation
How to think about this question
In a DNS amplification attack, the attacker uses a small query (e.g., 60 bytes for a 'ANY' record) that triggers a response many times larger (e.g., 4000 bytes), achieving an amplification factor of up to 70x. Open resolvers that recursively answer queries for any client are essential; the attack exploits their lack of source-IP validation. Real-world examples include the 2016 Dyn DDoS attack, which used DNS amplification to disrupt major internet services.
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
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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 amplification reflection denial-of-service. — This is a classic DNS amplification reflection DDoS attack. The attacker sends small DNS queries with a spoofed source IP (the victim's address) to open resolvers, which then send large DNS responses to the victim, overwhelming its bandwidth. The NetFlow data shows the server receiving many large DNS responses while only sending tiny spoofed queries, confirming the amplification and reflection vectors.
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.
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Last reviewed: Jun 11, 2026
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