[kh99]

It doesn't look like that's possible. You can have a user group that can't use groups at all, but there doesn't seem to be any way to configure a group to be visible to members only. (I could have missed it, in which case I'm sure someone will let us know )

You might be able to fake it. I created a plugin using hook group_start_postcheck and this code:

PHP Code:

if (!empty($group) AND empty($group['membertype']) AND in_array($group['groupid'], array(1, 2, 3)))
{
    print_no_permission();
} 


and that gives a "you have no permission" if you try to view a group with id 1, 2, or 3 and you're not a member. It doesn't hide the existence of the group (it still shows up in the list of groups). And it seems to work for any access through group.php but I don't know if there's any other way to view group messages that might have to be handled separately.