Cancelbots

Sometimes people post things to newsgroups which they should not. This includes spam, severely off-topics messages, flames, duplicate and other similar messages. Administrators of newgroups often have the power to delete these messages when desired.

However, since the messages have been propagated to thousands (or more) newsgroups servers, it is difficult if not impossible to simply delete them. Removing the message from a single server would be futile, since it would still exist on the remaining servers.

A special robot called a Cancelbot is used to cancel messages. A cancelbot is a special program which searches through newsgroups looking for messages which match specific patterns. Those messages that match are marked as "canceled", which more or less means they are marked for deletion. Newsgroup servers will no longer serve those messages and for all intents and purposes they have ceased to exist.

A newsgroup administrator with the appropriate privileges can trigger one of these robots on demand. Most people who read newsgroups are thankful this is done, because otherwise a group tends to fill up with spam and other undesirable messages very quickly. Some people, however, disagree because they feel this is censorship.

Robot cancelbots (known as robocancellers) are automated cancelbots which scan newsgroups periodically for spam messages. These robots use a series of rules to determine which messages are and are not spam. Those determined to be spam are canceled.