By default, public blog entries are made public to BeachBoard users as well as to the world wide web. If you would like for your blog entries to be public to BeachBoard users only, then you will need to disable the Availability option in your Settings. Disabling the blog Availability means that you cannot share your blog outside of BeachBoard.
To disable the availability of your Blog:
The External link for your blog will no longer appear and anyone who had that link will no longer be able to view your Blog unless they are a BeachBoard user.