Hi there
I am new to Simple Machines I have a problem that guest users can view all topics. When they go to my site they cant see anything but when they get a hold on a URL and they click on it they can view the topic
Check out this mod for read topic permission
http://mods.simplemachines.org/index.php?mod=231
You can also set different membergroup view board permissions and don't let groups who shouldn't be able to view the forum.