K9 / K9webprotection is a free Internet filter. They are made by Bluecoat, which is their commercial product, which is used in enterprise/corporate environments.
It’s customizable to block web sites in more than 70 categories, force SafeSearch on all major search engines, set time restrictions,
Configure custom lists for “always allow” and “always block”
Override a web page block with password
Trust the enhanced anti-tampering, even children can’t break
View easy reports to monitor and control web activity
Real-time categorization of new adult and malicious sites
Best free parental controls software/internet filter available
Compatible with Windows or Mac machines