According to Google and its Postini Message Security network, the volume of global spam traffic has risen by 156% since November 2008, when a large source of the world’s spam, the McColo network, was taken offline. Some other trends, noted in the Google blog entry:
- Spam volume peaked in April 2008
- Spam has not yet recovered to its November 2008 but may do so soon
- During the second half of 2008, virus volume increased six-fold from the first half of the year.
http://googleenterprise.blogspot.com/2009/01/2008-year-in-spam.html