A few of you requested that there would be an easier way to identify which forum is accessible by specific usergroups. This has now been implemented through a color coding system.
You will now see the applicable color code by each forum on the forum homepage:
And you will also see the color code when viewing threads:
Also yes, I ripped off Homeland Security.
Added January 2, 2012:
Additionally, you will see a static label in the bottom left of every forum, thread, new thread page and new reply page indicating the security level of the section you are currently operating in:
^ In this example, the forum which is currently being observed is a public section.