Generally, there are two parts to the filtering process. The first part involves rating the content or website, and the last step involves filtering the content or website. Rating The process of rating involves placing a value judgment to categorize websites based on their content. There are a variety of different tricks that such software uses to filter. Most products rely on an encrypted list of blocked sites or rely on keyword blocking.
Some products use even more advanced schemes to filter.
The software using lists of blocked sites must rely on the software company to regularly update the list of blocked sites. These lists are created and updated by either humans, computer, or a combination of both that search the Internet for certain keywords. Users must upload the latest list update regularly. In addition, some software includes an option for keyword blocking, which is used to keep children from seeing objectionable words. If the website has content that is not satisfactory or does not have the proper PICS rating, then the user is informed that access is denied and the content of the website is not displayed.