August 22, 2006 2:31 PM PDT

Worm sparks rise in zombie PCs

Malicious code that exploits a recent Windows hole has led to significant growth in the number of hijacked PCs, according to messaging security company CipherTrust.

On Tuesday, CipherTrust reported a 23 percent growth in the total number of so-called zombie PCs it has detected. The jump is due to the spread of Mocbot worm variants, CipherTrust said. Mocbot, also known as Cuebot and Graweg, exploits a Windows security flaw for which Microsoft issued a patch with security bulletin MS06-040 on Aug. 8.

"Around Aug. 13, the weekend after Black Tuesday, we started seeing a gradual increase in the average number of new zombies," said Dmitri Alperovitch, a research scientist at CipherTrust in Alpharetta, Ga. "It went up from 214,000 every day in the previous week to 265,000 every day."

Any computer infected by Mocbot will become part of a botnet, a large network of compromised PCs that can be controlled remotely to carry out tasks such as sending spam. In June, Microsoft warned that the threat posed by botnets and zombies was growing fast.

CipherTrust can trace the increase in spam-sending zombies to Mocbot by comparing junk e-mail sent by systems it knows were compromised by the worm to the spam sent by new zombies, Alperovitch said. "They are mostly Rolex spam and porn spam, and they are the same messages that are being sent by these new zombies coming online," he said.

Alperovitch estimated that somewhere between 500,000 and 1 million machines were hijacked by Mocbot. As a result, more junk mail is soiling the Internet, with spam making up 81 percent of all mail volume this week. "I would not say this has been a huge outbreak, but it has been a noticeable change," he said.

Security experts had said that the MS06-040 worm appeared to be limited in its spread and only hitting computers running Windows 2000.

Colin Barker of ZDNet UK reported from London.

See more CNET content tagged:
CipherTrust Inc., zombie, spam, worm, security


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ISPs don't seem to care about zombies
I report a lot of spam to the source ISP (using Most spam seems to come from dynamic IP addresses, indicating they are sent by zonbie PCs. It doesn't seems that ISPs are doing much to deal with these sources of spam in their networks.

I also reported several time that is a spammer that operates a network of zombie PCs (and charges money for their use). It doesn't seem that the host of this site cares, and these spammers continue to market their illegal services through this site. (And they don't just advertise porn/viagra. They have serious clients such as non-profit organizations that also receive government funding. So mainstream advertising money now goes into this botnet business).
Posted by hadaso (468 comments )
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Patch. Patch the patch. Patch the patches patch.
If you use Microsoft products, this is what you get regardless of defenses in place.
Posted by extinctone (214 comments )
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