Last Topics rights

I have a forum with 2 sections: a public one and a private one, only for members, (where the rights to see what's inside are given by Admin)
I have also a portal with a Last Topics window. My problem is that every topic that appear in this window can be read by anyone (just click on it), even it is a topic written in the private section. Can I restrict the access to reading these topics only for members? Of course, I want to keep in the Last topics window all the last topics (private or public)

if topics are private, they shouldn't be visible in that last topics window.