SY0-701 Threats, Vulnerabilities, and Mitigations Practice Question
A public website is overwhelmed by a flood of DNS responses arriving from many open resolvers after the attacker sends small forged queries to those resolvers. The target bandwidth is saturated and the source IPs vary widely. What kind of attack is being used?
⚠ Common exam trap
Watch out — candidates often confuse a DNS amplification attack with a SYN flood because both involve flooding, but the key differentiator is the use of DNS responses from open resolvers versus incomplete TCP handshakes.
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 DDoS
B is correct because this scenario describes a DNS amplification DDoS attack. The attacker sends small forged DNS queries with a spoofed source IP (the victim's IP) to open resolvers, which respond with much larger DNS replies. The flood of amplified responses saturates the victim's bandwidth, and the varying source IPs make mitigation difficult. This matches the description of a reflection/amplification attack using DNS.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
SYN flood
Why it's wrong here
A SYN flood targets TCP handshake state, but this scenario is centered on DNS responses from third-party resolvers.
- ✓
DNS amplification DDoS
Why this is correct
DNS amplification uses small spoofed requests to trigger much larger replies from reflectors, multiplying traffic toward the victim.
- ✗
Replay attack
Why it's wrong here
Replay attacks resend captured legitimate messages, but they do not create a large reflected response stream from resolvers.
- ✗
Man-in-the-middle attack
Why it's wrong here
A man-in-the-middle intercepts or alters traffic between parties, but the described symptom is bandwidth exhaustion from reflected traffic.
Visual reference
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Related to this question
Learn chapter
DoS and DDoS Attacks
Key term
DNS
DNS is the system that translates human-friendly domain names like example.com into machine-readable IP addresses so computers can find each other on a network.
Key term
Denial-of-service
A Denial-of-service (DoS) attack is an attempt to make a computer, network, or online service unavailable to its intended users by overwhelming it with fake traffic or requests.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SY0-701 practice question is part of Courseiva's free CompTIA 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 SY0-701 exam.