The spam industry is recovering quickly from last November's shutdown of  the world's largest junk e-mail network, according to Google's Enterprise Blog [1].

Worldwide spam dropped an incredible 70 percent late last year after U.S. authorities shut down servers operated by McColo Corp. of San Jose, California.

Since then, however, spam is up 156 percent. While that growth rate is expected to slow, spam will still likely rise to McColo-era levels within a few months, according to the blog.

This begs the question: Where will spam levels top off in 2009?

The best indicator, argues Google, is previous history. Despite McColo's demise late in the year, spam levels for 2008 still exceeded 2007's by 25 percent.

"All indicators suggest this trend will continue," forecasts Google, "as virus, malware, and link-based attacks become both more frequent and more ingenious."

Google's threat assessment for 2009 cautions Web users to remain vigilant against viruses sent via e-mail and in blended attacks, which combine e-mail and the Web. The second half of 2008 saw viruses increase by 600 percent over the first half of the year. For the most part, viruses were packed into legitimate looking e-mails or were held on Websites that users traveled to because they clicked on links in spoofed e-mail news alerts.

All in all, Google expects spammers will adapt to unload new viruses and malware. The company urges Web users to keep up-to-date on their virus detection and blocking technologies.

"Despite eliminating a major source, spam keeps coming back," Google says. "Spammers are re-investing with increasing speed to evolve their systems into decentralized, harder-to-detect ecosystems."