This thread is pretty old, especially since there have been many changes to BP over the 7 months since it was first started. But, there are some good hints about what you can do.
Please remember that the bp-custom.php file should be placed in /wp-content/plugins/ and not /mu-plugins/ as is mentioned early on in the thread. When the thread was first started, that location was correct. But not anymore.
https://buddypress.org/forums/topic/securing-components-from-non-logged-in-users
New thread? What? I can see only wordpressfan’s post above yours…..
@Paul
Haha!
By saying, “This thread is pretty old”, I meant the thread to which I was about to provide the link. I did not mean this thread as in this actual thread!