A cancelbot is an automated or semi-automated process for sending out third-party cancel messages over Usenet, commonly as a stopgap measure to combat spam.[1]
One of the earliest uses of a cancelbot was by microbiology professor Richard DePew, to remove anonymous postings in science newsgroups.[2] Perhaps the most well known early cancelbot was used in June 1994 by Arnt Gulbrandsen within minutes of the first post of Canter & Siegel's second spam wave,[3] [4] as it was created in response to their "Green Card spam" in April 1994.[5] 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:[6]
| Pseudosite | Criterion | ||
|---|---|---|---|
| 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: