Integrated Windows Authentication - Overview

Overview

Integrated Windows Authentication uses the security features of Windows clients and servers. Unlike Basic or Digest authentication, initially, it does not prompt users for a user name and password. The current Windows user information on the client computer is supplied by the browser through a cryptographic exchange involving hashing with the Web server. If the authentication exchange initially fails to identify the user, the browser will prompt the user for a Windows user account user name and password.

Integrated Windows Authentication itself is not a standard or an authentication protocol. When IWA is selected as an option of a program (e.g. within the Directory Security tab of the IIS site properties dialog) this implies that underlying security mechanisms should be used in a preferential order. If the Kerberos provider is functional and a Kerberos ticket can be obtained for the target, and any associated settings permit Kerberos authentication to occur (e.g. Intranet sites settings in Internet Explorer), the Kerberos 5 protocol will be attempted. Otherwise NTLMSSP authentication is attempted. Similarly, if Kerberos authentication is attempted, yet it fails, then NTLMSSP is attempted. IWA uses SPNEGO to allow initiators and acceptors to negotiate either Kerberos or NTLMSSP. Third party utilities have extended the Integrated Windows Authentication paradigm to UNIX, Linux and Mac systems.

For technical information regarding the protocols behind IWA, see the articles for SPNEGO, Kerberos, NTLMSSP, NTLM, SSPI, and GSSAPI.