I have made a section in my forum, for " known users" and I have made sure only known users and above can see the forums in it..... but it doesn't work... if I go to private browser, and not logged in, you can see the post that is in the secret section.

You can't see the forum, when you're no logged in, so that works, it's just the posts shows in the side bar. Which I don't want it to do, unless you're a known user