Table of Contents
http://meta.wikimedia.org/wiki/MediaWiki_FAQ#Basic_User_Account_Management.3F http://meta.wikimedia.org/wiki/Access_Restrictions#1.5_Upwards
In order to prevent readings from anonymous users you need to set (in /LocalSettings.php):
# Disable reading line, for anonymous (not-logged-in => * ) : $wgGroupPermissions['*']['read'] = false;