Apparently, messages from the FBI and CIA are the way to spread worms, a security firm said Thursday as it tallied up Sober's wildfire spread during November and concluded that the outbreak was the biggest ever.

E-mail security provider Postini said that it had quarantined more than 218 million Sober-infected messages in the last seven days, more than four times the 50 million-message average that it blocks in a run-of-the-mill month.

"This Sober generated close to a 1500 percent increase in virus-infected email traffic in the past week,” said Scott Petry, vice president of products and engineering at Postini, in a statement...........