A few years ago FB made a change to how it works so now I can view the profiles of those who are friends-of-friends even if I have NO idea who they are. It used to be that you could only view the profiles of those who were your friends. Why they changed that I have no idea and it didn't seem to be common knowledge. I have checked all of the various security settings and it isn't obvious to me if there is any way to eliminate that feature. Part of the reason I rarely post there anymore.