Virus, spam and other types of content filtering services are nowadays essential components of security solutions both in home and in production environments. Spam, viruses, trojans, malicious scripts pose a significant threat to the users through e-mails, downloadable files, or even simple webpages. Firewalls are a logical location for content filtering, as all traffic must travel across the firewall, and usually this is the earliest point where the incoming traffic can be examined and interacted with. CF provides an integrated framework to manage the various available Content Filtering components using a single, uniform interface.

The sections of this chapter provide an in-depth description of CF. For a basic overview of the CF framework, Content Filtering and a list of the supported modules, see Section 2.1.6, The concept of the CF framework.