Open source web filtering is used in many businesses and schools to block inappropriate or time-wasting websites, so students and employees can concentrate on learning and working. Administrators should always check the open source license that comes with an open source web filtering program, because many stipulate that commercial or business use is prohibited. When administrators are updating the program's blacklists, they should pay extra attention to finding proxy websites, because many people use these to sneak around filters. While web filters are supposed to block harmful or unnecessary websites, they sometimes block too much, so administrators also should focus on developing a whitelist. Web filters usually come with a pre-installed list of blocked websites, but some users may find a website that should on the list, but is not; to avoid problems stemming from this, administrators should scan history reports and add new websites to the blacklist as needed.
Most open source web filtering programs are used in businesses, but this may be a problem. Many open source licenses do not allow commercial or business use of the web filter, meaning the business can end up involved in a lawsuit if the use is discovered. To avoid this possibility, administrators should carefully read the licensing agreement before deploying the filter over a network.
When a web filter is in place, it is told to place restrictions on computers with certain Internet protocol (IP) addresses. If a user is able to change his or her IP address by using a proxy, then he or she effectively dodges all the open source web filtering restrictions. Many web filters quickly and automatically update their proxy website blacklist, but administrators should look out for new proxy websites and ensure they are on the list.
Web filters sometimes do their job too well and block a website that is not harmful or inappropriate; even worse, they may block a website that is essential for users to perform their work. This possibility means administrators should develop an open source web filtering whitelist. The whitelist, as opposed to the blacklist, is a list of websites that can be accessed by users, even if the websites would normally be blocked.
An open source web filtering program typically comes packed with millions of restricted websites, and it is uncommon for a user to stumble on a website that should be blocked but is not. At the same time, administrators should go through network history reports, just to check for the use of any inappropriate websites. If any websites are found, they should be added to the web filter blacklist.