Module 3 · S3 Security and Misconfigurations

Manish Garg
Manish Garg Associate of (ISC)² · RingSafe
Apr 19, 2026
7 min read
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Last updated: April 29, 2026

Amazon S3 is the single cloud service that has caused more publicly-disclosed breaches than any other — by a wide margin. Hundreds of millions of records from financial institutions, healthcare organisations, government agencies, and consumer apps have leaked from misconfigured S3 buckets.

Amazon S3 is the single cloud service that has caused more publicly-disclosed breaches than any other — by a wide margin. Hundreds of millions of records from financial institutions, healthcare organisations, government agencies, and consumer apps have leaked from misconfigured S3 buckets. Every single incident was preventable with settings available in the AWS console.

This module is the S3 security practitioner’s guide. You’ll learn what breaks, why, and every layer of defence that has to be configured properly.

Why S3 specifically

S3’s design makes it the ideal data-exfil target:

  • Object storage is where data lives — backups, exports, logs, datasets, uploads
  • Buckets are globally addressable by name — once found, they’re reachable from anywhere
  • S3 has been around since 2006; lots of legacy configurations
  • Access controls are layered (IAM, Bucket Policy, ACL, Block Public Access) — multiple opportunities for misconfig
  • Bucket contents are often discoverable via predictable naming (companyname-backups, companyname-dev)
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