Have you tried using the Forum Access module? I'm not sure if it can hide the link for you, but it should be able to handle the other parts, making it so that unregistered users can't even see the forum posts.
You might want to check out Taxonomy Access and Taxonomy Access Lite. That with the forum access module are great closing off parts of the forums. It just depends on exactly what you want to do.
Check out http://www.lullabot.com/articles/private_forums_in...
Matt Farina
Geeks and God Co-Host
www.mattfarina.com
We want to restrict forum access except to registered users that are in our Bible study class. Its easy enough to remove the navigation link to it and restrict un registered users to post, but we dont even want the url to be available unless the person is logged in. I have done this with our Bible study audio thanks to you guys, but cant figure out how to make it work for the forums.
Have any input on this?