Directory services are widespread throughout major computer networks. A Lightweight Directory Access Protocol (LDAP) directory is an example of this type of service. LDAP directories are special databases that usually contain usernames, passwords, common names, e-mail addresses, business addresses, and other attributes. Organizations first used directory services to facilitate the distribution of address books and user information. Since that time, directory services have grown to take on roles as the central repositories for all user information and authentication services.