Integrated Windows Authentication (IWA)[1] is a term associated with Microsoft products that refers to the SPNEGO, Kerberos, and NTLMSSP authentication protocols with respect to SSPI functionality introduced with Microsoft Windows 2000 and included with later Windows NT-based operating systems.
When IWA is selected as an option of a program (e.g. within the Directory Security tab of the IIS site properties dialog)[7] this implies that underlying security mechanisms should be used in a preferential order.
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.
It may work with other web browsers if they have been configured to pass the user's logon credentials to the server that is requesting authentication.