[acronym, ‘Automated Retroactive Minimal Moderation’] A Usenet cancelbot created by Dick Depew of Munroe Falls, Ohio. ARMM was intended to automatically cancel posts from anonymous-posting sites. Unfortunately, the robot's recognizer for anonymous postings triggered on its own automatically-generated control messages! Transformed by this stroke of programming ineptitude into a monster of Frankensteinian proportions, it broke loose on the night of March 30, 1993 and proceeded to spam news.admin.policy with a recursive explosion of over 200 messages.

ARMM's bug produced a recursive cascade of messages each of which mechanically added text to the ID and Subject and some other headers of its parent. This produced a flood of messages in which each header took up several screens and each message ID and subject line got longer and longer and longer.

Reactions varied from amusement to outrage. The pathological messages crashed at least one mail system, and upset people paying line charges for their Usenet feeds. One poster described the ARMM debacle as “instant Usenet history” (also establishing the term despew), and it has since been widely cited as a cautionary example of the havoc the combination of good intentions and incompetence can wreak on a network. The Usenet thread on the subject is archived here. Compare Great Worm; sorcerer's apprentice mode. See also software laser, network meltdown.