1. A computer-readable storage medium excluding signals having computer-executable instructions for implementing a method of authenticating and authorizing an extranet client to a secure intranet business application via a perimeter network, wherein connections to the secure intranet business application from the perimeter network or the extranet are not permitted, the computer-readable medium comprising: computer executable instructions for registering an extranet client with a secure intranet business application within the secure intranet by mapping an extranet identification of the extranet client to a business application identification corresponding to the extranet client, wherein the business application identification is associated with a business application client within the secure intranet, and wherein a perimeter network proxy corresponds to both the extranet identification of the extranet client and the business application identification mapped to the extranet client identification; computer executable instructions for receiving an impersonation session request from the perimeter network including a perimeter network proxy identification of a perimeter network proxy corresponding to an authenticated extranet client; computer executable instructions for authenticating the perimeter network proxy identification within the secure intranet by verifying the existence of the perimeter network proxy identification in a business application directory within the secure intranet; computer executable instructions for using the business application identification to acquire business application client information from the associated business application client within the secure intranet when the perimeter network proxy identification is successfully authenticated; computer executable instructions for creating an impersonation session with the secure intranet business application for the authenticated extranet client by using the perimeter network proxy corresponding to the authenticated extranet client to impersonate the business application identification mapped to the authenticated extranet client, such that the perimeter network proxy: impersonates the business application client associated with the business application identification, executes the secure intranet business application with the business application identification of the authenticated extranet client according to the acquired business application client information, and the secure intranet business application receives requests from the extranet client using the impersonation session and processes the requests as the extranet client; and computer executable instructions for transmitting information relating to the impersonation session to the perimeter network.