Customers of Amazon’s Cloud computing platform AWS can control user access to resources through the Identity and Access Management feature available with the service. Using IAM you can create and manage AWS users and groups and use permissions to allow and deny their permissions to AWS resources.
For more details how to implement and construct an AWS Identity and Access Management (IAM) policy with folder-level permissions for Amazon S3 buckets or coding IAM Policies, I suggest the following blog:
Read more here – http://blogs.aws.amazon.com/security/blog