The TL;DR is that this time, we ended up discovering ~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.

Naturally, we registered them, just to see what would happen - “how many people are really trying to request software updates from S3 buckets that appear to have been abandoned months or even years ago?”, we naively thought to ourselves.

A new ransomware campaign encrypts Amazon S3 buckets using AWS's Server-Side Encryption with Customer Provided Keys (SSE-C) known only to the threat actor, demanding ransoms to receive the decryption key.

Without altering a single line of code, attackers poisoned the NPM package “bignum” by hijacking the S3 bucket serving binaries necessary for its function and replacing them with malicious ones