What is impersonation?
Impersonation is when a user gains access to a resource by using a different identity, usually as an anonymous user. To allow this, Windows uses a special user account known as the anonymous logon account. Whenever an attempt is made to access server resources over the Web, the user is automatically logged on anonymously. The user can only access the resources for which the anonymous user account has privileges. By default, the username for the anonymous logon account takes the form IUSR_COMPUTERNAME, in which COMPUTERNAME is the name of the server.