2025-02-04
Abandoned AWS S3 Buckets Risk Supply Chain Attacks
Watchtowr labs has published analysis of their discovery of "~150 Amazon S3 buckets that had previously been used across commercial and open source software products, governments, and infrastructure deployment/update pipelines - and then abandoned." The researchers purchased the empty buckets for a total of $420.85 and received "more than 8 million HTTP requests over a 2 month period," including but not limited to requests for: software updates, "pre-compiled (unsigned!) Windows, Linux and macOS binaries," virtual machine images, JavaScript files, CloudFormation templates, and SSLVPN server configurations. The requests arrived from around the globe, including from government networks and agencies, military networks, Fortune 100 and 500 companies, major payment card networks and financial institutions, universities, casinos, and companies in the cybersecurity, software, and industrial product sectors, among others. The researchers emphasize the malicious potential of this position, positing that it "could have led to supply chain attacks that out-scaled and out-impacted anything we as an industry have seen so far," including SolarWinds. AWS has since worked with Watchtowr to sinkhole all the S3 buckets involved in the research, but "Amazon did not say why it doesn't ban the reuse of S3 bucket names, which is what watchTowr says would be the easiest way to fix the issue."
Editor's Note
Imagine if you would, a software product with the update source hard coded, which gets decommissioned, then someone else comes along and re-registers that bucket and starts providing "enhanced" updates. Part of the problem is that S3 buckets are in a global namespace, so while permissions restrict access, any of us can create a specific bucket name if it is available. Watchtowr researchers have proposed AWS implement changes to prevent re-use of bucket names; whether or not that gets implemented, make sure that you're following current AWS S3 bucket best practices.

Lee Neely
Congrats to Watchtowr for the excellent research and responsible reporting. This also serves as a great reminder for organizations to 'know their environment.' That means knowing and managing what hardware and software assets are on your network, including cloud resources. It's also the reason why the CIS Critical Security Controls have Controls 1 and 2. I would include Control 3, Data Protection in this reminder. Finally, it's also an opportunity to discuss with your cloud service provider their processes for reuse of terminated infrastructure.
