Stratosphere: Finding Vulnerable Cloud Storage Buckets

Misconfigured cloud storage buckets have leaked hundreds of millions of medical, voter, and customer records. These breaches are due to a combination of easily-guessable bucket names and error-prone security configurations, which, together, allow attackers to easily guess and access sensitive data. In this work, we investigate the security of buckets, finding that prior studies have largely underestimated cloud insecurity by focusing on simple, easy-to-guess names. By leveraging prior work in the password analysis space, we introduce Stratosphere, a system that learns how buckets are named in practice in order to efficiently guess the names of vulnerable buckets. Using Stratosphere, we find wide-spread exploitation of buckets and vulnerable configurations continuing to increase over the years. We conclude with recommendations for operators, researchers, and cloud providers.