Online's Unholy Alliance.(hackers teamed with spammers)

Here's how it might happen. While weeding out the morning's spam, you stumble upon one e-mail message that gives you pause. Perhaps it looks like a note of reconciliation from an old girlfriend, or the sender happens to have the same name as your real stockbroker. In a moment of weakness, you open it. Nothing happens, or so you think. Unwittingly, without even opening an attachment, you've allowed a virus surreptitiously to turn your computer into one of an army of "zombies" that broadcast offers of black-market Viagra and get-rich-quick schemes to millions of people.

The stereotypical virus writer has always been a lonely hacker bent on causing maximum disruption. Lately, though, hackers seem to have teamed up with spammers, those twilight Internet advertisers who count on one sucker in a million to go for porn sites, penis-enlarging pills and various snake-oil products. Last week's SoBig virus has convinced many security experts that viruses are the latest method of circumventing anti-spamming measures. "If you think about the motives of virus writers a year or two ago, it was all about recognition," says Brian Czarny, marketing director at MessageLabs, an Internet security firm. "What's the motivation today? It's much different: there's money involved."

SoBig instructed each of the estimated 145,000 computers it infected to download software from one of 20 computers in the United States, Canada and South Korea. Because security officials intervened, we'll probably never know for sure what was ...