"It's a result of the dramatic spread of bot networks," says Lloyd Taylor, VP of technology and operations for Internet performance-monitoring company Keynote Systems Inc. Bot networks consist of up to hundreds of thousands of computers on which hackers have placed apps called bots or zombies that can be commandeered to attack any system or network connected to the Internet. Security software vendor Symantec Corp. says it's tracking a half-million systems with bots on them.
The DoubleClick and Microsoft attacks come on the heels of a major attack in June against several Akamai Technologies Inc.'s customer Web sites. Those who control bots also are gaining increased access to compromised systems to steal system owners' identities, rent out their bot networks, and work with spammers to use those systems to distribute junk E-mail, Taylor warns. "It can be quite lucrative."