Spam senders suffered a few temporary setbacks in 2008, including an FTC bust on HerbalKing, one of the largest global spam networks allegedly responsible for sending billions of unsolicited emails, and the shuttering of web host McColo Corp, who the FTC said was responsible for roughly 75 percent of the world's spam. It may have taken a few months, but spam levels have now risen back up to 150 percent, according to Postini Message Security.

"As spammers fill the void left by McColo, it's reasonable to anticipate a decreasing rate of growth as spam reaches November 2008 levels," wrote Amanda Kleha of the Google message-security team on the company's blog. "However, since the November levels weren't even the peak for the year, and since spammers appear to be quickly recovering, the question remains: Where will spam volume top out in 2009? Will it be near the November 2008 level? The April 2008 level? Or higher?"

Symantec also notes a concerning rise in spam, noting that it has seen spam volumes return to within 5 percentage points of the pre-McColo shutdown numbers. In other words, the break is over and barring another bust, spam levels could rise even higher than what they were before a series of crackdowns took place.