Ref Password Protect guessbook

I notice in the admin options you can password protect your guestbook..i have marked the option and it is still letting any and everyone leave comments in my guest book. I want to be able to send subjects a password and they be the only one able to leave a message...is that not possible?

Whats the point in a guestbook if only certain people can post? The clue is in the title, GUESTbook. The only way you could stop just anyone posting is to password protect the addentry.php file.