You wouldn't be able to do it as long as the user has access to [[Profile folder]], lack of which makes Firefox not able to work - the user would be able to delete any data. Even prior to private browsing feature, history was clear-able in ''Tools'' - '' Clear recent history'' window. To have more control, you can block some websites/ports in the router or firewall, the [https://addons.mozilla.org/en-US/firefox/addon/4351/ FoxFilter] add-on can be helpful (but again, the users can simply un-install it).