I have an ASP.NET MVC 1.0 application that uses Forms Authentication. We are using Windows Server 2008. I need to lock down the site so that only certain users (in AD Groups) can access the site. Unfortunately, though, when I set the site to not allow anon users and use windows authentication, due to the integration of the site and IIS, it shows the user as signed in as their domain account, instead of allowing them to sign in through Forms Auth.

So, I need a mixed mode authentication. I need the site to be only accessible through windows auth, without anon users, but once you are in, it needs to use forms auth only. How would I go about doing this the right way?