We have a few thousand Win2k users who access a portal. The portal is
hosted on WebLogic portal. Currently I have it setup using IIS so that
when a user hits the portal, the user gets authentication via IIS and
IIS passes that information to WebLogic. Effectively users do not need
to enter their username password.

I need to setup the same procedure (single sign-on I guess) with
WebLogic. I know siteminder exists for this purpose, but need to know
whether it can be performed via WebLogic simply by implementing a
plug-in or additional module.

Any input would be highly appreciated.