Spam levels, which fell sharply when botnet host McColo was taken down in November, will bounce back to pre-McColo levels by the end of January, according to Google's Adam Swidler.

Swidler, who handles Google's (NASDAQ: GOOG) business-to-business e-mail security offerings, told that more attacks will be launched to grow botnets (define) and that there will be an increase in Web-based attacks. Businesses have to make sure they focus on security, Sidler warned.

Meanwhile, spammers are using the latest technology to avoid detection and survive parts of their botnets being shut down, Swidler said.

"When McColo was shut down, the industry saw spam levels fall 70 percent," Swidler said. "We'd never seen anything like that dramatic level of drop in such a short time."

McColo had hosted a large number of botnet command-and-control centers, the servers that managed botnets, and, when it was taken down, there was no way for them to send out spam.

However, spammers began recovering from the blow within weeks. The Google Message Security data center, which only measures business to business e-mail, saw spam levels jump by mid-January to 156 percent of the volume that existed the day after McColo was shut off, Swidler said.

According to Swidler, spammers are working hard to grow their botnets again.

Spammers will launch attacks to create botnets in two ways, he said. One is the traditional attack where malware is attached to e-mail and the spammer tries to get the user to click on it. Such malware will seem to be a notice from a bank or a delivery message from a courier company, Swidler said.

The other will be a blended threat, where links are embedded in e-mails. E-mails used in this attack will look like a credit offering or a get rich quick scheme or a news item, Swidler said. One of the most notorious such attacks, purporting to be a CNN News item about the fighting in Gaza, was launched earlier this month.

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