The correct actions are enabling S3 Block Public Access and applying a bucket policy with a Deny effect. S3 Block Public Access acts as a security override that prevents any public access to the bucket, regardless of other permissions, while a bucket policy with an explicit Deny statement ensures that unauthorized users—even those with broad IAM permissions—are blocked from accessing sensitive data. On the AWS Certified Data Engineer Associate DEA-C01 exam, this pairing tests your understanding of defense-in-depth for data protection: Block Public Access is a blanket safeguard, while a Deny policy provides granular control. A common trap is confusing logging services like S3 server access logs or CloudTrail with preventive controls—they only audit, not block. Remember the memory tip: "Block the public, Deny the rest" to recall that both layers are needed for robust S3 data protection.
DEA-C01 Data Security and Governance Practice Question
This DEA-C01 practice question tests your understanding of data security and governance. 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.
Which TWO actions should a data engineer take to protect sensitive data in an Amazon S3 bucket from being accessed by unauthorized users? (Select TWO.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add a bucket policy with a Deny effect for unauthorized principals
Options A and C are correct. Option A (S3 Block Public Access) prevents public access to the bucket. Option C (bucket policy with Deny effect) explicitly denies access to unauthorized users. Option B (S3 server access logs) is for auditing, not prevention. Option D (CloudTrail) is for logging, not prevention. Option E (VPC endpoint) is for network connectivity, not access control.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Create a VPC endpoint for S3
Why it's wrong here
VPC endpoints provide private connectivity, not access control.
✗
Enable S3 server access logging
Why it's wrong here
Server access logs are for auditing, not preventing access.
✓
Add a bucket policy with a Deny effect for unauthorized principals
Why this is correct
A Deny policy explicitly denies access.
Related concept
Standard ACLs match source addresses.
✗
Enable AWS CloudTrail for the bucket
Why it's wrong here
CloudTrail logs API calls, it does not prevent access.
✓
Enable S3 Block Public Access
Why this is correct
Block Public Access prevents public access to the bucket.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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.
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DEA-C01 ACL questions on filtering logic and placement.
Data Security and Governance — This question tests Data Security and Governance — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Add a bucket policy with a Deny effect for unauthorized principals — Options A and C are correct. Option A (S3 Block Public Access) prevents public access to the bucket. Option C (bucket policy with Deny effect) explicitly denies access to unauthorized users. Option B (S3 server access logs) is for auditing, not prevention. Option D (CloudTrail) is for logging, not prevention. Option E (VPC endpoint) is for network connectivity, not access control.
What should I do if I get this DEA-C01 question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related DEA-C01 ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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