The answer is SYN cookies. This is the most effective mitigation technique because SYN flood attacks exploit the TCP three-way handshake by flooding a server with SYN packets from spoofed IPs, leaving the server waiting for final ACKs that never arrive and filling its connection queue with half-open connections. SYN cookies work by encoding connection state information into the initial sequence number of the SYN-ACK response, allowing the server to avoid storing any state for incomplete handshakes until the final ACK is verified, thus preserving memory and processing capacity. On the Certified Ethical Hacker CEH exam, this concept tests your understanding of network-layer DDoS mitigation and the TCP handshake vulnerability; a common trap is confusing SYN cookies with rate limiting or blackholing, which are less surgical. Remember the mnemonic: “Cookies keep the queue clean.”
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 SOC analyst observes a high number of incomplete TCP connections with the SYN flag set but no corresponding ACK from the target. The source IPs are spoofed and the connections are targeting port 80 on a web server. Which DDoS mitigation technique would be MOST effective in this scenario?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
SYN cookies
SYN flood attacks exploit the TCP three-way handshake by sending many SYN packets without completing the handshake. SYN cookies allow the server to avoid storing half-open connections, effectively mitigating SYN floods.
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.
✓
SYN cookies
Why this is correct
SYN cookies encode connection state in the SYN-ACK, allowing the server to avoid resource allocation until the handshake completes.
Related concept
Read the scenario before looking for a memorised answer.
✗
Rate limiting
Why it's wrong here
Rate limiting can reduce traffic, but SYN cookies specifically address incomplete handshakes.
✗
Anycast distribution
Why it's wrong here
Anycast distributes traffic across multiple data centers but does not prevent SYN exhaustion.
✗
Ingress filtering
Why it's wrong here
Ingress filtering blocks spoofed IPs at the network edge, but the attack is already occurring.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 practitioner preparing for the CEH exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CEH question in full detail.
Identify which CEH exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Malware, Social Engineering and Network Attacks — This question tests Malware, Social Engineering and Network Attacks — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: SYN cookies — SYN flood attacks exploit the TCP three-way handshake by sending many SYN packets without completing the handshake. SYN cookies allow the server to avoid storing half-open connections, effectively mitigating SYN floods.
What should I do if I get this CEH question wrong?
Identify which CEH exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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