The e-mail-using world rejoiced in November when the McColo network was busted and spam levels dropped 70 percent. But spam levels are now back up 150 percent, according to Postini Message Security.

What does that mean? Spammers are recovering, and it's likely that total spam volumes will return to pre-McColo levels within just a few months.

"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?"

Ever-Increasing Spam

Kleha suggested that one way to answer that question is by comparing 2008 overall levels with previous years. Spam threats rose visibly during the year, reflecting the overall trend of rising attacks. Even with the drop in November, spam levels climbed 25 percent over 2007.

"Our statistics show that the average unprotected user would have received 45,000 spam messages in 2008, up from 36,000 in 2007," Kleha said. "All indicators suggest this trend will continue as virus, malware and link-based attacks become both more frequent and more ingenious."

Looking ahead to the rest of 2009, Google expects viruses sent via e-mail and in blended attacks -- e-mail and Web -- to continue to be a serious threat. During the second half of 2008, virus volume increased sixfold from the first half of the year. Google warned that we can also expect viruses and malware to continue to be a key tool and area of focus for spammers to upgrade their platforms.

"Of course, the only thing we can really say with certainty about 2009 is that spam and viruses will continue to be unpredictable," Kleha said. "And given that uncertainty, virus-detection and blocking technologies become even more important."

Increasingly Complex Spam

Dermot Harnett, principal analyst of antispam engineering for Symantec, offers a different perspective. Since 2006, spam volumes have risen significantly -- from 55 percent of mail volume in September 2006 to more than 80 percent of mail volume (up until the McColo shutdown on Nov. 11, 2008).

"With the McColo shutdown, spam volumes dropped significantly. The Symantec Probe Network saw a 65 percent drop in traffic when comparing the 24 hours prior to the McColo.com shutdown to the 24 hours after," Harnett confirmed.

However, in recent days Symantec has seen spam volumes returning to the pre-McColo level. Spam levels are within five percentage points of their pre-McColo shutdown numbers.

"As the spam volume has returned, it is important to remember that spam is becoming increasingly complex," Harnett said. "Spammers continue to innovate to find new spam vectors to deliver their messages, both attempting to evade antispam filters and by making the spam messages look more legitimate."