What is a permissions boundary in IAM?

A permissions boundary in Identity and Access Management (IAM) functions as an advanced feature that sets the maximum permissions that can be granted by an identity-based policy. This means it acts as a limit on the permissions that users or roles can obtain, regardless of the permissions that are defined in the policies attached to them.

When a permissions boundary is applied, it establishes a security boundary around the permissions that are granted through the user or role’s policy, ensuring that even if their policies would normally grant wider access, the permissions boundary restricts their actual capabilities to those allowed by the boundary. This is particularly useful for enforcing granular control over permissions in complex environments and ensuring compliance with organizational security policies.

This feature helps organizations manage permission levels effectively, ensuring that identities cannot exceed their designated level of access, which is crucial for maintaining a secure environment.