Misconfigured S3 buckets: data exposed to the world

Amazon S3 is private by default, but misconfigurations open it: public ACLs, permissive bucket policies, or "Authenticated Users" access (which means any AWS account, not yours).

The problem

A public bucket can be listed and downloaded without credentials. Even without listing, predictable names (company-backups) are guessable. Public writes let attackers alter content served to users.

aws s3 ls s3://bucket --no-sign-request
aws s3 sync s3://bucket ./loot --no-sign-request

Defence

Block Public Access at the account level (the switch that shuts it all). Least-privilege policies, no Principal:*. Encryption at rest, versioning, and access logging. Continuous scanning (AWS Config, tools like CloudMapper) to find exposures.