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 Sobig climbs the top in 2003
December 5, 2003
Unless a surprise pops up in the last weeks of 2003, the Sobig e-mail worm that flooded the Net in August will be the most widely spread virus of 2003, regarding from a top ten list of viruses recently published by antivirus software vendor Sophos PLC.
Sophos virus ranks based on the number of infection reports it receives from customers, revealed that the Sobig-F version accounted for almost 20% of virus reports to Sophos in 2003, taking out its closest rival, the Blaster worm, with 15%.
Nachi (aka Welchia), the most accounted of the Blaster derivatives, took the third spot on the list, followed by Gibe at fourth and Dumaru in the fifth.
Unlike Blaster, Sobig used e-mail to spread and generated huge volumes of e-mail traffic once it started to infect machines. All those e-mail messages caught the attention of both home users and companies, some of which reported receiving hundreds of thousands of infected messages a day, according to Sophos.
"Blaster was an Internet worm, so if people applied the necessary Microsoft patches, they didn't get infected. With Sobig, the flow of e-mail was there regardless of whether you had the proper software patches and antivirus updates," said Carole Theriault, a security analyst at Sophos.
Sophos itself received more than 400,000 Sobig e-mail messages within the first 24 hours after the worm appeared in the wild, she said. Several days after that, Sophos received tons of calls from customers, which vaulted Sobig-F, the sixth version of the worm to appear on the Internet, to the top of the list.
However, telling the exact number of infected systems from the number of phone calls is difficult, if not impossible, she said.
"It's difficult to say 'this many people were infected,' and that can be misleading. There are a lot of people infected with Sobig now who don't know it and are continuing to spread the virus," Theriault said.
Other prominent virus outbreaks like Slammer didn't make the list, though they were ranked high at first, reports of infections dropped off quickly because home users and organizations rapidly patched system vulnerabilities.
All of the top ten viruses were aimed at Microsoft Windows operating system, a trend that Sophos predicts will continue in 2004.
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