使用IIS / Active Directory控制对网站的访问

I need to secure a legacy help site on our network that points out to the world. Ideally, I want to have people authenticate with their active directory logins, because everybody in the company is already there, and they already know that stuff. Ideally, I'd need to set the default domain so people don't have to type that.I need to secure a legacy help site on our netw