The answer is the `aws:SourceVpc` condition key in a VPC endpoint policy. This condition is correct because it restricts access to your S3 buckets so that requests must originate from a specific VPC, effectively locking down data flow to only the S3 VPC endpoint and blocking any exfiltration attempts over the public internet. On the AWS Certified Cloud Practitioner CLF-C02 exam, this tests your understanding of network-level security controls versus IAM user permissions—a common trap is confusing `aws:SourceVpc` with `aws:SourceIp` or thinking a bucket policy alone is enough. Remember, the endpoint policy acts as a gatekeeper at the network boundary, not at the user level. Memory tip: think “Source VPC” as “Source Virtual Private Cloud” to keep it tied to network origin, not IP addresses.
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 wants to protect their S3 buckets from accidental or malicious data exfiltration by ensuring that data can only leave the VPC through S3 endpoint conditions. Which IAM policy condition controls this?
Why wrong: Block Public Access prevents public access to S3 — it doesn't restrict access to a specific VPC or prevent credential misuse from outside the VPC.
B
VPC endpoint policy with aws:SourceVpc condition
The `aws:SourceVpc` or `aws:SourceVpce` condition in an S3 bucket policy restricts access to only requests coming through a specific VPC or VPC endpoint, preventing exfiltration via compromised credentials outside the VPC.
C
S3 CORS configuration
Why wrong: CORS controls cross-origin browser access to S3 — it doesn't restrict API-level access based on network origin.
D
Amazon Macie sensitive data classification
Why wrong: Macie discovers and classifies sensitive data — it doesn't enforce network-level access restrictions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
VPC endpoint policy with aws:SourceVpc condition
Option B is correct because the `aws:SourceVpc` condition key in a VPC endpoint policy restricts access to S3 buckets so that requests must originate from the specified VPC. This ensures that data can only leave the VPC through the S3 VPC endpoint, preventing accidental or malicious data exfiltration via the public internet. By combining this condition with a VPC endpoint policy, the company enforces network-level control over S3 access.
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.
✗
S3 Block Public Access
Why it's wrong here
Block Public Access prevents public access to S3 — it doesn't restrict access to a specific VPC or prevent credential misuse from outside the VPC.
✓
VPC endpoint policy with aws:SourceVpc condition
Why this is correct
The `aws:SourceVpc` or `aws:SourceVpce` condition in an S3 bucket policy restricts access to only requests coming through a specific VPC or VPC endpoint, preventing exfiltration via compromised credentials outside the VPC.
Related concept
Read the scenario before looking for a memorised answer.
✗
S3 CORS configuration
Why it's wrong here
CORS controls cross-origin browser access to S3 — it doesn't restrict API-level access based on network origin.
✗
Amazon Macie sensitive data classification
Why it's wrong here
Macie discovers and classifies sensitive data — it doesn't enforce network-level access restrictions.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse S3 Block Public Access (a bucket-level permission control) with network-level exfiltration prevention, or they mistakenly think Macie or CORS can enforce data flow restrictions, when only VPC endpoint policies with the `aws:SourceVpc` condition can restrict traffic to a specific VPC.
Detailed technical explanation
How to think about this question
The `aws:SourceVpc` condition key works with VPC endpoint policies to evaluate the source VPC ID of a request, ensuring that only traffic from the designated VPC can access the S3 bucket. This is enforced at the network layer via the VPC endpoint's route table, which directs S3 traffic through the endpoint rather than the internet gateway. In a real-world scenario, this prevents data exfiltration even if an IAM role has broad S3 permissions, because the request must originate from the VPC and cannot bypass the endpoint via a public IP.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CLF-C02 question in full detail.
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: VPC endpoint policy with aws:SourceVpc condition — Option B is correct because the `aws:SourceVpc` condition key in a VPC endpoint policy restricts access to S3 buckets so that requests must originate from the specified VPC. This ensures that data can only leave the VPC through the S3 VPC endpoint, preventing accidental or malicious data exfiltration via the public internet. By combining this condition with a VPC endpoint policy, the company enforces network-level control over S3 access.
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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