Sandcastle is a Python-based Amazon AWS S3 Bucket Enumeration Tool, formerly known as bucketCrawler. The script takes a target’s name as the stem argument (e.g. shopify) and iterates through a file of bucket name permutations.
Amazon S3 [Simple Storage Service] is cloud storage for the Internet. To upload your data (photos, videos, documents etc.), you first create a bucket in one of the AWS Regions. You can then upload any number of objects to the bucket.
Source: drak net org
Sandcastle – AWS S3 Bucket Enumeration Tool