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To hide their tracks, spammers have always misappropriated the computers of innocent third parties. But the rise of Windows zombies is arguably the gravest problem facing spam opponents today. By one estimate, over 60 percent of junk e-mail now originates from home PCs that spammers have commandeered with the help of virus writers and hackers.
With an ever-growing arsenal of Windows zombies under their control, spammers can evade some spam filters, which have trouble keeping current lists of the addresses of known zombie systems. What's more, spammers have used their networks of zombied computers to launch denial-of-service attacks on sites operated by blacklist services and other anti-spam organizations. ...
Microsoft's anti-spam initiatives may be hampered, however, by what Prince and other experts describe as the firm's split personality over junk e-mail. Microsoft's MSN and Hotmail services appear determined to run spammers off their networks on a rail. But the company's other business units want to preserve Microsoft's ability to use unsolicited e-mail in, for example, cross-marketing to existing customers.
Mircrosoft’s failure to make security a priority is threatening the whole Internet.