NCSA httpd allows you to control who can access different document trees on your server. It also allows you to define which server functions are carried out in different document trees.
Note that the following methods of access limitation can work independently, or be combined.
Host filtering is used to limit document trees to certain machines, most likely local machines or those directly involved in a project.
If your browsers are using a browser that supports user authentication, like Mosaic 2.0 for X, you can have browsers authenticate themselves with a user name and a password before they are able to access protected documents.
httpd@ncsa.uiuc.edu