Open source content filter programs are an essential part of maintaining a business, school or any other institution where the Internet is available, because they censor inappropriate websites. While most open source content filter programs offer the same core features, some features will be required for advanced filtering, while others will make it easier to maintain the filter overall. A dynamic content filter is one that can search out new websites that should be blacklisted, and automatically do so. A blacklisted website may need to be accessed at some point, and filters that can open the one website without having to shut down completely are preferred. Proxy filtering and image filtering also are important.
New websites come out all the time with games, chat and other features that businesses and schools want to block in a bid to keep employees or students productive. While most open source content filter programs have a large index of blacklisted websites and the list is usually updated periodically, it is possible that someone can access a non-blacklisted website. A dynamic filter will look at keywords and files on the website and, if it deems the website inappropriate, will add that website to the blacklist and cut off access.
Websites are blacklisted because they should not be accessed at any time, but it may sometimes be necessary to use one of these websites. For example, if a business partner needs to be contacted quickly and he or she can only be reached through a social networking website, then the filter will need to be lifted. Some filters will have to turn off the entire filter and, in the meantime, other employees or students will have open access to normally banned websites. It is better if the open source content filter can open access to the one website without lifting the whole filter.
To get around an open source content filter, many employees or students use an anonymous proxy. This masks the Internet protocol (IP) address of the computer and replaces it with a different one, so the filter does not recognize the IP address. Being masked means the computer is able to bypass the filter. The filter program should come with an index of proxy websites to ensure no one bypasses the filter.
Image filtering is an uncommon but important feature for many open source content filter programs. If someone is able to get around the filter, he or she may be able to open inappropriate images. An image filter scans the image for potential problems and may be able to censor the image.
