Yea, there has been some inquiries to do something like this as well as a totally closed board to guests.
For example classic used to allow you to set it as a closed board to guests. This is not in the 7.x version.
I have kinda lost track of the v8.x changelog but I don't recall this being in the log.
In v7.x about the only thing to turn off per group is in site permissions.
Can see the shoutbox
Can use the Search Engine
Can view Member Profiles
Can view the Member List
It would be nice to enhance what is accessible by group.
