- A
Security Groups
Why wrong: Security Groups are stateful and operate at the instance level (elastic network interface), not at the subnet level. They cannot be used to control traffic for an entire subnet with a single rule set.
- B
Network ACLs
Network ACLs are a stateless firewall operating at the subnet level, supporting both inbound and outbound rules. They evaluate traffic based on rule order and allow or deny traffic without maintaining connection state, matching the requirement.
- C
AWS WAF
Why wrong: AWS WAF is a web application firewall that works at Layer 7 to protect against common web exploits. It does not provide subnet-level network firewall capabilities and is not designed for general network traffic control.
- D
AWS Shield
Why wrong: AWS Shield is a managed DDoS protection service that safeguards applications against distributed denial-of-service attacks. It does not function as a subnet-level firewall with inbound/outbound rule evaluation.
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 company is deploying a three-tier web application on AWS. The security team requires a network-level firewall that operates at the subnet level and can evaluate both inbound and outbound traffic using stateless rules. Which AWS feature should the company use to meet this requirement?
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 ACLs
Network ACLs (NACLs) are a stateless, subnet-level firewall that evaluates both inbound and outbound traffic based on numbered rules. Unlike security groups, NACLs do not maintain connection state, so rules must be explicitly defined for both directions, meeting the requirement for stateless inspection at the subnet boundary.
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 operate at the instance level (elastic network interface), not at the subnet level. They cannot be used to control traffic for an entire subnet with a single rule set.
When this WOULD be correct
A question asks for an instance-level firewall that automatically allows return traffic (stateful) and requires no explicit outbound rules for responses. Security Groups would be the correct choice.
- ✓
Network ACLs
Why this is correct
Network ACLs are a stateless firewall operating at the subnet level, supporting both inbound and outbound rules. They evaluate traffic based on rule order and allow or deny traffic without maintaining connection state, matching the requirement.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
AWS WAF
Why it's wrong here
AWS WAF is a web application firewall that works at Layer 7 to protect against common web exploits. It does not provide subnet-level network firewall capabilities and is not designed for general network traffic control.
When this WOULD be correct
A company needs to protect a web application from common web exploits like SQL injection or cross-site scripting (XSS) by filtering HTTP/HTTPS requests to an Application Load Balancer or CloudFront distribution.
- ✗
AWS Shield
Why it's wrong here
AWS Shield is a managed DDoS protection service that safeguards applications against distributed denial-of-service attacks. It does not function as a subnet-level firewall with inbound/outbound rule evaluation.
When this WOULD be correct
A company needs to protect its web application from DDoS attacks and requires always-on detection and automatic inline mitigations to minimize application downtime. AWS Shield Standard or Advanced would be the correct answer.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The CLF-C02 exam frequently reuses these exact scenarios with slightly different constraints.
✓Network ACLsCorrect answer▾
Why this is correct
Network ACLs are a stateless firewall operating at the subnet level, supporting both inbound and outbound rules. They evaluate traffic based on rule order and allow or deny traffic without maintaining connection state, matching the requirement.
✗Security GroupsWrong answer — click to see why▾
Why this is wrong here
Security Groups operate at the instance level, not the subnet level, and use stateful rules, whereas the requirement specifies a subnet-level, stateless firewall.
★ When this WOULD be the correct answer
A question asks for an instance-level firewall that automatically allows return traffic (stateful) and requires no explicit outbound rules for responses. Security Groups would be the correct choice.
Why candidates choose this
Candidates often confuse Security Groups with Network ACLs because both are firewalls, but they forget that Security Groups are stateful and instance-level, not subnet-level and stateless.
✗AWS WAFWrong answer — click to see why▾
Why this is wrong here
AWS WAF is a web application firewall that operates at Layer 7 (application layer) and uses stateful rules to inspect HTTP/HTTPS traffic, not a network-level firewall at the subnet layer with stateless rules.
★ When this WOULD be the correct answer
A company needs to protect a web application from common web exploits like SQL injection or cross-site scripting (XSS) by filtering HTTP/HTTPS requests to an Application Load Balancer or CloudFront distribution.
Why candidates choose this
Candidates may confuse 'firewall' with 'web application firewall' (WAF) and overlook the specific requirements for network-level, stateless, subnet-level filtering.
✗AWS ShieldWrong answer — click to see why▾
Why this is wrong here
AWS Shield is a managed DDoS protection service, not a network-level firewall. It does not operate at the subnet level or provide stateless rule evaluation for inbound and outbound traffic.
★ When this WOULD be the correct answer
A company needs to protect its web application from DDoS attacks and requires always-on detection and automatic inline mitigations to minimize application downtime. AWS Shield Standard or Advanced would be the correct answer.
Why candidates choose this
Candidates may confuse AWS Shield as a firewall because it provides traffic filtering and protection, but it is specifically for DDoS mitigation, not general network access control.
Analysis generated from the official CLF-C02blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing stateful security groups (which automatically track connection state) with stateless network ACLs, leading candidates to choose Security Groups when the question explicitly requires stateless, subnet-level filtering.
Detailed technical explanation
How to think about this question
NACLs support numbered rules from 1 to 32766, evaluated in ascending order, with an implicit deny-all rule at the end. Each rule can specify protocol (e.g., TCP, UDP, ICMP), port range, and CIDR block, and because NACLs are stateless, you must configure separate inbound and outbound rules for ephemeral ports (typically 1024-65535) to allow return traffic. In a real-world scenario, a misconfigured NACL can silently drop all traffic if the outbound ephemeral port range is not opened, causing connectivity issues that are hard to debug.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
Visual reference
What to study next
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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 ACLs — Network ACLs (NACLs) are a stateless, subnet-level firewall that evaluates both inbound and outbound traffic based on numbered rules. Unlike security groups, NACLs do not maintain connection state, so rules must be explicitly defined for both directions, meeting the requirement for stateless inspection at the subnet boundary.
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.
About these practice questions
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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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