When it comes to identity management, a directory is a repository of accounts. An account represents an entity with attributes and an identity to identify it uniquely. Password, as an authenticator, is the most commonly implemented authentication factor, something you know, so password breach results in a severe business impact.

Protecting passwords at rest, in transit, and in use is crucial. The account database can exist as a system file, registry, data structure in the memory, backup file in tapes, or in any ephemeral or persistent form in any storage. Understanding how operating systems store, convey, and cache authenticators (the password itself or its derivatives) for authentication is critical to minimizing the attack vectors and surface.