Headless PHP Drupal script deletes spam zombie user accounts

For for the last few months automatic bots have been creating hundreds of zombie accounts per day on the TurnKey web site. I'm not sure why they bother. I assume it has something to do with spamming, but they never log in. Besides, spam almost never gets past our content filter (Mollom) and when it does we always nuke it. Zero tolerance.

Brains...

Meanwhile these zombie accounts are polluting my precious database, and that bothers me. Besides, call me prejudiced, but I just hate zombies. You're either alive or you're dead. Pick a side!