Dennis

Protect your BuddyPress Installation from strangers. Only registered users will be allowed to view the installation and all other users will be redirected to the login page. Users attempting to view blog content via RSS are also authenticated via HTTP Auth.
You can exclude the registration, the homepage and blog pages (e.g. posts, archives and non-buddypress pages) from protection. In combination with the plugin ‘Invitation Code Checker’ your installation stays private but the registration is for users with a special password open.
The plugin includes a German and Hebrew (thanks to gstupp) translation.

Private BuddyPress

Protect your BuddyPress Installation from strangers. Only registered users will be allowed to view the installation.

fpoller

Gives the following options for making the WordPress installation more private:
<ul>
<li>Protect content from being viewed to users who hasn’t logged in</li>
<li>Disable all feeds</li>
<li>Only serve uploaded files to logged in users</li>
<li>IP address based exceptions for the above options</li>
</ul>

Private WP suite

Adds option in the admin panel for making your blog (including rss feeds and uploaded files) private.

Private BuddyPress vs Private WP suite