9.2. Authentication vs. Authorization
Two important security principles in use within a domain are authentication and authorization. In short, authentication is used to identify a user, and authorization is used to control access of the user.
As an example, if Joe is given a domain account, he can log on with that account. He uses it for authentication. However, just because Joe can log on doesn't mean he's automatically granted access to all the resources in the domain. Instead, his account is granted access to specific resources based on his needs and what he's authorized to access.
9.2.1. Authentication
Authentication is used to prove a user's identity. In general, there are three factors of authentication:
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