/etc/cups/cupsd.conf
# Restrict access to the server...
<Location />
Allow @LOCAL
Order allow,deny
Allow localhost
</Location>
# Restrict access to the admin pages...
<Location /admin>
Allow @LOCAL
Encryption Required
Order allow,deny
Allow localhost
</Location>
# Restrict access to configuration files...
<Location /admin/conf>
Allow @LOCAL
AuthType Basic
Require user @SYSTEM
Order allow,deny
Allow localhost
</Location>