PICS[14] is a system that enables labels to be associated with web pages and other Internet content. It was originally designed to help control the Internet content that children have access to, but it can also be used for other labels such as code signing and privacy. PICS is ideal for web filtering since its labels can be used by filters to determine what type of content is being requested. Content with labels that match a certain criteria can be rejected by a filter.
Without a system such as PICS, it is very difficult to block access to certain types of Internet content. For example, without PICS, it is almost impossible to block access to adult-oriented content on the web. Attempts are made to block web sites with certain hostname or filename patterns, but with over 3 million web addresses[16] this is a very difficult task. With PICS however, adult-oriented content can be labelled as such and blocked when necessary.
PICS hasn't had wide-scale success so far, but there are many web sites that provide PICS labelled content. There are also several PICS capable web browsers and a few PICS filtering proxy servers.