Cleanfeed is a spam filter for use with Usenet news groups. As well as blocking spam, it is also able to block binary image posts in non-binary news groups and HTML posts. It acts by looking for repeated patterns and duplicate messages, and is able to identify known spamming sites and domains. It is published by Red Hat and is freely distributable.

Cleanfeed is also the name of a content blocking system implemented by BT, claimed to be targeted only at illegal content identified by the Internet Watch Foundation, and which all UK ISPs will be obliged to implement a version of by the end of 2007. Information on how this works is restricted to members of the LINX. [http://publicaffairs.linx.net/news/?p=154