E2Guardian is a powerful open source web content filter that provides users with the ability to control access to the Internet. It is designed to protect networks from inappropriate web content, malware, and other threats. It blocks access to inappropriate web sites, as well as sites hosting malicious content, and can also be used to restrict access to specific types of online activities. It can be used to filter content based on keywords, file type, or other criteria. It also provides customizable reports and logging options, allowing administrators to monitor user activity. E2Guardian is available for Linux, Windows, and Mac OS X systems.
Discontinued Last updated in 2012: https://sourceforge.net/projects/dansguardian/files/