An Amazon EC2 instance is running an application that uses Amazon Simple Queue Service (Amazon...

The most secure way for an EC2 instance to access AWS services is by using an IAM role attached to the instance. IAM roles eliminate the need for long-term credentials, which reduces the risk of credential leakage and simplifies credential rotation.

Following the principle of least privilege, the IAM policy attached to the role should grant only the permissions required: sqs:SendMessage, sqs:ReceiveMessage, and sqs:DeleteMessage. Granting broader permissions such as sqs:* violates least privilege and increases security risk.

Options A and B rely on IAM users and static credentials, which are not recommended for applications running on EC2. Option C grants excessive permissions.

Therefore, attaching an EC2 IAM role with only the required SQS permissions is the most secure solution.