LH Private BuddyPress is a simple, single mission plugin with no settings to change, you install and activate it and it immediately turns your BuddyPress site into a private network in so much as once it is active then any attempt by a non logged in user to access any of the BuddyPress pages will be redirected to the login page.
BuddyPress Activity Filter is a useful plugin that allows you to customise the the way the BuddyPress activity feed works. It allows site admins to limit which filters are available on the activity page, limit which activity filters are available on the main site-wide activity page and customise the activity updates for each post type.
BuddyPress Registration Groups is a plugin that adds a list of groups to the registration form so that new members can be introduced and join your groups. It means they don’t need to go looking for them to be instantly tied in to their preferred groups. Adding this kind or form to your registration can help you to build a profile for each new member.