DEA-C01 Data Security and Governance Practice Question

A data engineer needs to grant an IAM user read-only access to an S3 bucket named 'data-lake'. Which IAM policy statement should be used?

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

✓

{"Effect":"Allow","Action":["s3:ListBucket","s3:GetObject"],"Resource":["arn:aws:s3:::data-lake","arn:aws:s3:::data-lake/*"]}

It allows ListBucket on the bucket and GetObject on objects, enabling read-only access. Option A is wrong because it grants write actions (PutObject, DeleteObject). Option B is wrong because it allows all S3 actions (s3:*). Option D is wrong because it only allows ListBucket, not GetObject.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
{"Effect":"Allow","Action":["s3:PutObject","s3:DeleteObject"],"Resource":"arn:aws:s3:::data-lake/*"}
Why it's wrong here
This statement grants write and delete permissions, directly contradicting the read-only requirement, and omits s3:GetObject entirely. It would suit a role needing to modify objects in the bucket. Read-only access requires allowing s3:GetObject and s3:ListBucket on the bucket and its objects.
✗
{"Effect":"Allow","Action":"s3:*","Resource":"*"}
Why it's wrong here
Granting s3:* on all resources provides full S3 administrative access far beyond read-only, violating least privilege. Such wildcard policies suit temporary administrative or break-glass roles. The scenario demands only s3:GetObject and s3:ListBucket scoped to the data-lake bucket and its objects.
✓
{"Effect":"Allow","Action":["s3:ListBucket","s3:GetObject"],"Resource":["arn:aws:s3:::data-lake","arn:aws:s3:::data-lake/*"]}
Why this is correct
The policy pairs bucket-level `s3:ListBucket` with object-level `s3:GetObject`, mapping each action to the correct ARN: `arn:aws:s3:::data-lake` for the bucket itself and `arn:aws:s3:::data-lake/*` for its objects. This satisfies the read-only requirement, since listing needs bucket scope while retrieval needs object scope.
✗
{"Effect":"Allow","Action":"s3:ListBucket","Resource":"arn:aws:s3:::data-lake"}
Why it's wrong here
s3:ListBucket alone permits listing object keys but not retrieving object contents, so reads of actual data fail. This action suits scenarios where only bucket inventory visibility is needed. Read-only access also requires s3:GetObject on arn:aws:s3:::data-lake/*.

Quick reference

AWS S3 Storage Class Comparison

Storage Class	Min Duration	Retrieval	Use Case
S3 Standard	None	Immediate	Frequently accessed data
S3 Standard-IA	30 days	Immediate	Infrequent access, rapid retrieval
S3 One Zone-IA	30 days	Immediate	Non-critical infrequent data
S3 Intelligent-Tiering	None	Immediate–hours	Unknown or changing access patterns
S3 Glacier Instant	90 days	Milliseconds	Archive with instant retrieval
S3 Glacier Flexible	90 days	Minutes–hours	Archive, flexible retrieval
S3 Glacier Deep Archive	180 days	Hours	Long-term compliance archive

Go deeper

DEA-C01 Data Security and Governance Practice Question

Why each option matters

Option-by-option breakdown

AWS S3 Storage Class Comparison

Related to this question