Access Analyzer for S3 is a new feature that monitors your access policies, ensuring that the policies provide only the intended access to your S3 resources. Access Analyzer for S3 evaluates your bucket access policies and enables you to discover and swiftly remediate buckets with potentially unintended access.

from Recent Announcements: https://aws.amazon.com/about-aws/whats-new/2019/12/introducing-access-analyzer-for-amazon-s3-to-review-access-policies/