A user account is a record that consists of all the information that defines a user to Microsoft Windows Server 2003. This includes the user name and password required for the user to log on, the groups in which the user account has membership, and the rights and permissions the user has for using the computer and network and accessing their resources. A user account provides a user with the ability to log on to a computer to gain access to resources on that computer or to log on to a domain to gain access to network resources. Each person who regularly uses a computer or the network should have a unique user account.

In Windows Server 2003, authentication for domain users is based on user accounts in Active Directory. Authentication confirms the identity of any user trying to log on to a domain or to access network resources. Windows Server 2003 authentication enables single sign-on to all network resources. With single sign-on, a user can log on to the client computer once, using a single password or smart card, and authenticate to any computer in the domain. To provide security for a network running Windows Server 2003, you must provide access for legitimate users but screen out potential intruders. This means you must set up your security features to authenticate all user access to system resources. Authentication protects against intruders trying to steal identities or impersonate users.