Hello Veedoo !

You may also disable all actions for Unauthenticated users in Permissions level - it will hide the detailed content of your site from guests. Other variants include the code changes (not good for the auto-upgrades) or database mass-changing in the table `sys_object_pages` like with the next query (backup this table first):

UPDATE `sys_object_pages` SET `visible_for_levels`='510'