I belong to a closed group on facebook, so yes only people who are part of the group can see the content. But I would think that people would still be smart AND NOT PUT THE ADDRESS OF THE NEW HOME THEY ARE MOVING INTO AND THE DAY THEY ARE MOVING INTO IT on the internet. Because, anyone can join a freaking closed group. It's not like I had to give blood to join the group. I clicked request to join group and I was approved.