Menu item only visible after login

On my website i have a closed part and public part. I would like to have both the menu-entry as the pages beneath it only visible when logged-in.

Untill now i manage to have the spe ific pages hidden when logged-out, but the menu option stayes visible. This is causing pages notfound messages when you try to reach that page.

What is best way of approach to have those pages/menu items hidden when not logged-in?