I use smbauth to check if the users NT-username and password match...
I have to say that i dont know much about iis security. I submit username and password and get the information if they match. Then i process this information in my application.
I found a binary that seems to do just what i need: http://www.armcad.narod.ru/userserver.zip
will look into it within the next hours
cheers,
Jochen