A web content filtering system is something that sits between the client computers and the internet, and restricts access to certain websites based on criteria. It can either be inline, where the requests are sent directly through the content management system, or passive, where the content management listens in "promiscuous" mode for those certain sites. If a site that is deemed unacceptable is found, the content management system sends a TCP RST packet to the other end, and hijacks the web session to redirect it to the block page. Content Management Systems can be used by parents or administrators to block innapropriate sites to minors, or to only allow certain sites deemed acceptable.
