Two days after actor Heath Ledger died, e-mails began moving across the Web purportedly carrying a link to a detailed police report divulging “the real reason” behind the actor’s death. Ledger had been summarily drafted into the service of a botnet.

Bots are compromised computers controlled by profit-minded crooks. Those e-mails were spread by a network of thousands of bots, called a botnet. Anyone who clicked on the link got instantly absorbed into the fast-spreading Mega-D botnet, says protection firm Marshal. Mega-D enriches its operators, mainly by distributing spam for male-enhancement pills.

Largely unnoticed by the public, botnets have come to inundate the World Wide Web. On a typical day, 40 percent of the 800 million computers connected to the Web are bots engaged in distributing e-mail spam, stealing sensitive details typed at banking and shopping Web sites, bombarding Web sites as part of extortionist denial-of-service attacks, and spreading fresh infections, says Rick Wesson, CEO of Support Intelligence,

a San Francisco-based company that tracks and sells threat input.

“It’s like a disease you can’t even feel,” Wesson says. “The mechanisms we use to protect our networks simply are not working.”

The botnet problem shows no sign of easing. shield firm Damballa pinpointed 7.3 million rare instances of bots carrying out nefarious activities on an average day in January — an astronomical leap from a daily average of 333,000 in August 2006. That included botnet-delivered spam, which accounted for 91 percent of all e-mails in early March, up from 64% last June, says e-mail management firm Cloudmark.

The upshot of that deluge is profound, whether not immediately obvious, says Adam O’Donnell, Cloudmark’s director of emerging technology. Telecoms and Net service providers must absorb the cost of carrying botnet traffic; they can be expected to pass that expense onto companies and consumers, he says. Meanwhile, tens of millions of…

Orginal post by Top Tech News