Security Question

I have a security question... I have all my permissions set at "members" only and when I'm logged onto my forum I have seen that there is a guest online a few times... This is making me nervous and I would like to know if they are just outside the forum and it shows up as a guest or are they really inside?

Here is a screen shot the private info is blacked out...



Also: I have their IP address... How can I get more information by using this address? I did look on the map that you can click on that pops up when you click on their IP address so I know what part of the world they are on but that is all I know how to do....

Any help would be so welcomed... This forum is set up as a private one...

as far as i am concerned, the guest are only viewing your 1st page.. the one they has to type in their user name and password or they have to register.. not in your forum.. anyway, i'm just a newbie here... anyone could clarify more bout this?