The answer is that a DNS amplification attack is a form of DDoS attack, characterized by the use of spoofed source IP addresses and open DNS resolvers to generate massive, amplified traffic directed at a victim. This works because the attacker sends small queries with the victim’s spoofed IP to an open resolver, which then returns a much larger response to the victim, overwhelming its bandwidth or resources. On the Certified Ethical Hacker CEH exam, this question tests your ability to distinguish between attack types—specifically, that DNS amplification is a volumetric DDoS technique, not a protocol-based attack like a SYN flood. A common trap is confusing amplification with reflection alone; remember that amplification specifically multiplies traffic volume, while reflection merely bounces it. For a quick memory tip, think “Spoof, Query, Amplify, DDoS”—the four pillars of this attack.
CEH Practice Question: Malware, Social Engineering and Network Attacks
This CEH practice question tests your understanding of malware, social engineering and network attacks. 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 network administrator notices unusual traffic patterns: the internal DNS server is receiving large DNS queries with the source IP spoofed to appear as the internal DNS server itself. The queries appear to be amplification requests. Which TWO characteristics describe this attack?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It relies on open DNS resolvers to amplify traffic
DNS amplification uses spoofed source IP and open resolvers to amplify traffic. The large response overwhelms the victim. It is a type of DDoS, not a protocol attack like SYN flood.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
It is a protocol-specific attack targeting TCP SYN packets
Why it's wrong here
SYN flood is a protocol attack; DNS amplification uses UDP.
✓
It relies on open DNS resolvers to amplify traffic
Why this is correct
Open resolvers respond with large records, amplifying traffic.
It requires the attacker to be on the same subnet as the victim
Why it's wrong here
Spoofed source IP can be from anywhere; no local subnet needed.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related CEH subnetting questions on CIDR, address ranges, and subnet selection.
Malware, Social Engineering and Network Attacks — This question tests Malware, Social Engineering and Network Attacks — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: It relies on open DNS resolvers to amplify traffic — DNS amplification uses spoofed source IP and open resolvers to amplify traffic. The large response overwhelms the victim. It is a type of DDoS, not a protocol attack like SYN flood.
What should I do if I get this CEH question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related CEH subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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Question Discussion
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