Yesterday (day 2) covered how to encrypt and preserve S3 data. Today we dig deep into the authorization layer that determines who accesses it. S3 access control involves multiple mechanisms evaluated together, and the exam relentlessly asks "given multiple policies exist simultaneously, what is the final result?" The core principle is explicit Deny always wins (IAM evaluation model) and enforcing encryption, transmission security, and network paths via policy conditions.
A request to access a single S3 object is evaluated by combining these mechanisms: