Overview
Both the main ASURA website and the "Help for Volunteers" website are mainly viewable by anyone, i.e., without any sort of sign-in.
The Help for Volunteers site has some content that is sensitive, and should be available only to those who need it. That content can be viewed only by volunteers who have been given permission. Those volunteers must sign in to the site to see the content.
A combination of user roles and content types are used to control access. These are both features of Drupal.