The best security practice when providing EC2 instances access to AWS services (like S3) is to use an IAM role with an instance profile. This avoids hardcoding secrets and enables automatic credential rotation.

“We strongly recommend that you use IAM roles for applications that run on Amazon EC2 instances to securely access AWS services.”

— IAM Roles for Amazon EC2

Benefits:

No manual credentials

Temporary and automatically rotated keys

Least privilege access via IAM policies

Incorrect Options:

A: Root user access is not to be used for programmatic access.

B: Storing secret keys is insecure and discouraged.

D: MFA/versioning improves object protection, not access control.