https://webhostinggeeks.com/howto/how-to-restrict-the-access-to-specific-web-sites-using-squid-proxy-server-on-centos-6-2/
https://www.linuxhelp.com/how-to-block-keywords-and-extensions-in-squid-2/
https://www.ghacks.net/2010/06/19/restrict-network-access-by-time-or-ip-address-with-squid/
https://serverfault.com/questions/249622/allow-facebook-access-only-in-specific-hours-of-the-day-with-squid