Wiktionary
cancelbot
n. (context computing Internet English) a bot that sends messages to Usenet newsgroups to remove certain postings, especially spam.
Wikipedia
Cancelbot
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.
Usage examples of "cancelbot".
Depending on the speed and effectiveness of any Pentagon interventions - roadblocks, packet assassins and cancelbots being just a few possibilities - there could be half a million copies or more in circulation by the time they found and shut down the source servers.