ufdbGuard is the fastest URL filter available for Squid. It does 25,000 URL verifications/sec on a 2.8 GHz CPU.

ufdbGuard is free and based on SquidGuard. You can download it at the home of ufdbGuard and SourceForge.

To use ufdbGuard you need to edit the squid.conf file and add the following lines:
redirect_program /local/squid/bin/ufdbGuard -c /local/squid/etc/ufdbGuard.conf redirect_children 2 More details about how to configure ufdbGuard can be found at home of ufdbGuard.

A URL filter needs a list of URLs of undesired web content. Such a list is referred to as a URLFilterDatabase.

ufdbGuard is Free software, licensed under the GPL. You can use one of the free URL databases or pay to have access to the commercial database of URLS to block (and updates to the list).