- A
Security groups
Why wrong: Security groups are stateful and applied at the instance/ENI level, not the subnet level. Return traffic is automatically permitted for allowed connections.
- B
Network Access Control Lists (NACLs)
NACLs are applied at the subnet level and are stateless — each packet is evaluated against the rules independently. Both inbound and outbound rules must explicitly allow traffic, including return traffic for connections initiated from inside the subnet.
- C
AWS WAF
Why wrong: WAF operates at the HTTP/HTTPS application layer to block malicious web requests. It does not provide general subnet-level TCP/IP traffic filtering.
- D
VPC route tables
Why wrong: Route tables control where traffic is sent but do not filter traffic. They do not allow or deny packets based on port or protocol.
CLF-C02 Security and Compliance Practice Question
This CLF-C02 practice question tests your understanding of security and compliance. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 security engineer needs to apply network traffic filtering rules at the subnet level rather than the instance level. The solution must be stateless and must explicitly define both inbound and outbound rules, including allowing return traffic. Which AWS feature provides subnet-level stateless traffic control?
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
Network Access Control Lists (NACLs)
Network Access Control Lists (NACLs) are the correct choice because they operate at the subnet level, are stateless (meaning they do not automatically allow return traffic), and require explicit inbound and outbound rules. This matches the requirement for stateless traffic filtering where both directions must be defined separately, including rules for return traffic.
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.
- ✗
Security groups
Why it's wrong here
Security groups are stateful and applied at the instance/ENI level, not the subnet level. Return traffic is automatically permitted for allowed connections.
- ✓
Network Access Control Lists (NACLs)
Why this is correct
NACLs are applied at the subnet level and are stateless — each packet is evaluated against the rules independently. Both inbound and outbound rules must explicitly allow traffic, including return traffic for connections initiated from inside the subnet.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
AWS WAF
- ✗
VPC route tables
Why it's wrong here
Route tables control where traffic is sent but do not filter traffic. They do not allow or deny packets based on port or protocol.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse security groups (stateful, instance-level) with NACLs (stateless, subnet-level), forgetting that the stateless requirement explicitly demands separate inbound and outbound rules for return traffic.
Detailed technical explanation
How to think about this question
NACLs are stateless packet filters that evaluate rules in ascending order by rule number (from 1 to 32766) and apply an allow or deny decision based on the first matching rule. A common real-world scenario is when a subnet hosts a public-facing web server: you must explicitly add an inbound rule for HTTP (port 80) and a corresponding outbound rule for ephemeral ports (1024-65535) to allow return traffic, as NACLs do not track connection state. Under the hood, NACLs process traffic at layers 3 and 4 of the OSI model, inspecting source/destination IP addresses, protocols (TCP/UDP/ICMP), and port ranges.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
Visual reference
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Security and Compliance — study guide chapter
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FAQ
Questions learners often ask
What does this CLF-C02 question test?
Security and Compliance — This question tests Security and Compliance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Network Access Control Lists (NACLs) — Network Access Control Lists (NACLs) are the correct choice because they operate at the subnet level, are stateless (meaning they do not automatically allow return traffic), and require explicit inbound and outbound rules. This matches the requirement for stateless traffic filtering where both directions must be defined separately, including rules for return traffic.
What should I do if I get this CLF-C02 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
This CLF-C02 practice question is part of Courseiva's free Amazon Web Services 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 CLF-C02 exam.
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