There has been a significant observed drop in worldwide SPAM levels during the last month or so. M86 thinks it's due to Rustock, the world's largest spam botnet, suddenly stopped sending spam for unknown reasons. McAfee has expressed a different point of view. According to them, the steep drop in spam levels is due to recent attempts to shutdown Pushdo.D, another famous spam botnet. It's clear that spam levels are dropping, so let's look behind the curtain and try to find the actual reasons for the statistical observations.
I can think of two possible reasons why a major spam botnet would suddenly stop sending spam:
1. There was an attempt to shutdown the botnet by taking down its CnC servers.
2. The bot herders are running out of business i.e no one is paying them to send SPAM.
