Some clever, sexy Christmas-themed spam and a long holiday season helped the criminals behind the notorious Storm Worm more than double their network of infected PCs over the past few weeks, security experts say.
Storm kicked off its holiday spam-and-malware campaign on the day before Christmas, sending off a flurry of e-mail that invited victims to visit a Christmas-themed strip show on
Web sites such as Merrychristmasdude.com. Victims who downloaded the strip show found their PCs attacked by malicious software.
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This site, and about 14 other Storm-related domains, was registered using a Russian domain name registrar called Nic.ru, where staff was largely unavailable during the holidays, according to Richard Cox, the chief information officer with the
Spamhaus anti-spam effort.
"The trouble was they were quite simply out to Christmas lunch," Cox said. "And they didn't get back until Wednesday."
Spamhaus representatives tried to contact the registrar on Dec. 26, but they soon discovered that the company was essentially
shut down. Four days later they received an e-mail from a Nic.ru employee saying that they would have to wait until staff
returned to work in January before anything could be done, Cox said.
Storm's creators took advantage of another common problem in the domain name registration system. They targeted a registrar
that did not have an established policy for taking down malicious domains, so that gave the criminals a little more time to
run their scam, Cox said.
By Wednesday of this week, Nic.ru had removed the Storm-related domains from its database, knocking the criminal network's
Web sites offline.
But now security experts say that Storm has more than doubled in size, adding about 25,000 PCs to a network that had been
20,000 strong.
Storm's creators also changed the configuration of their malware, making it harder for security software to detect it, and
this helped inflate the number of infections, Cox said.
The Christmas campaign was "pretty effective at growing the botnet," said Jose Nazario, senior security engineer at Arbor
Networks. "The contributing factors there were clearly the successful timing, tied to a major Western holiday, coupled with
tweaks to the malware to avoid antivirus detection."
The IDG News Service is a Network World affiliate.
