One of the first recorded cancelbots was created in June 1994 by Arnt Gulbrandsen within minutes of the first post of Canter & Siegel's second spam wave, as it was created in response to Canter & Siegel's better known "Green Card spam" in April 1994.  Usenet spammers have alleged that cancelbots are a tool of the mythical Usenet cabal.
Cancelbots must follow community consensus to be able to serve a useful purpose, and historically, technical criteria have been the only acceptable criteria for determining if messages are cancelable, and only a few active cancellers ever obtain the broad community support needed to be effective.
Pseudosites are referenced in cancel headers by legitimate cancelbots to identify the criteria on which a message is being canceled, allowing administrators of Usenet sites to determine via standard "aliasing" mechanisms which criteria that they will accept third-party cancels for.
Currently, the generally accepted criteria (and associated pseudosites) are:
|Breidbart Index above the cancel threshold for the group or hierarchy||cyberspam!usenet|
|"Make money fast" schemes||mmfcancel!cyberspam!usenet|
|"Spew" (large number of nonsense or repeated postings)||spewcancel!cyberspam!usenet|
|Binary files posted to a group that doesn't allow them||bincancel!cyberspam!usenet|
|Retromoderation (only applies to groups that have a retromoderation policy in place)||retromod!cyberspam!usenet|
|Ad cancels within the biz.* hierarchy||adcancel!cyberspam!usenet|
|Messages originating from sites or networks under active Usenet Death Penalty (UDP) sanction by the community; the UDP is exceedingly rare, requiring a broad consensus that a Usenet site is acting in a manner generally harmful to the community, and active cancellation under a UDP is even rarer still||sitenameudp!udpcancel!cyberspam!usenet|
By general convention, special values are given in X-Canceled-By, Message-Id and Path headers when performing third-party cancels. This allows administrators to decide which reasons for third-party cancellation are acceptable for their site:
- The $alz convention states that the Message-Id: header used for a third-party cancel should always be the original Message-Id: with "cancel." prepended.
- The X-Canceled-By: convention states that the operator of a cancelbot should provide a consistent, valid, and actively monitored contact email address for their cancelbot in the X-Canceled-By: header, both to identify the canceler, and to provide a point of contact in case something goes wrong or questions arise regarding the cancelbot's operations.
- The !cyberspam convention states that specific pseudosites should be given within the cancel message's Path to identify them as complying with certain cancel criteria, see above.
- Scott Southwick; J.D. Falk. "The Net Abuse FAQ". Retrieved 2006-09-02.
- Canter, Laurence. "Green Card Lottery- Final One?". Retrieved 2006-09-02.
- Gulbrandsen, Arnt. "Now comes the C&S crunch... let's see". Retrieved 2006-09-02.
- Gulbrandsen, Arnt. "Canter and Siegel: What really happened".
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