According to Google, that's exactly what happened in 2008. After the rogue web hosting firm McColo was shut down in November, spam level dropped rapidly. By now, however, spam levels are rising again and are up by 156% since November. Google assumes that the total spam volume will return to pre-McColo takedown levels within just a few months.Spammers are a resilient bunch. Even if you manage to shut down one major spam network, others will gladly jump in and fill the void.
Even with the shutdown of McColo, however, overall spam levels in 2008 were 25% higher than in 2007. Based on the data from its Postini Message Security network, Google calculates that an unprotected user would have received close to 45,000 spam messages in 2008.
Looking Forward: More Viruses
For 2009, Google assumes that this upward trend will continue and possibly accelerate again, as malware and link-based attacks become more effective. During the second half of 2008, Google noticed that virus volume in email increases six-fold from the first half of the year. While the overall volume of these messages is still small, Google assumes that spammers will increasingly rely on these viruses to rebuild the infrastructure that became unavailable after the McColo shutdown.