The Breidbart Index, developed by Seth Breidbart ^[1], provides a measure of severity of newsgroup spam. The Breidbart Index is calculated over a 45-day window, and takes into account the number of newsgroups to which a message is posted. It is defined as the sum over each copy of the message of the square root of the number of newsgroups that copy is cross posted to. Articles are considered the same if they are substantively identical. Newsgroup spam is a type of spamming where the targets are Usenet newsgroups. ... A newsgroup is a repository usually within the Usenet system, for messages posted from many users at different locations. ... Crossposting is the act of posting verbatim copies of one message on multiple message centers, without customising each copy to suit the audience or forum. ...

For the Big 8 and alt.* hierarchies, it is generally agreed^[2] that messages are cancellable spam when the Breidbart Index exceeds 20, at which point they can be auto-cancelled from news servers. Other hierarchies have their own rules; many (smaller, local ones) are much more restrictive. A newsgroup is a repository usually within the Usenet system, for messages posted from many users at different locations. ...

See also

• Breidbart Index in Ursine's Jargon Wiki.

References

1. ^ Breidbart's initial post suggesting the 'square root' rule is at http://groups.google.com/group/news.admin.misc/msg/6e7f15c048a71019?dmode=source
2. ^ http://www.killfile.org/faqs/spam.html