Sobig.F worm 'biggest this year' but network effects 'negligible'

ISPs and antivirus vendors are claiming the Sobig.F worm, which has bombarded inboxes worldwide over the past week, is the most prolific virus to hit the Web this year. Despite a considerable increase in network traffic generated by the worm, ISPs have reported no problems with their e-mail servers or significant disruptions across their networks.

Telstra corporate affairs spokesperson Stuart Gray said he believed the Sobig.F variant to be the “biggest and fastest-acting virus this year”. Although the worm’s significance and scope is impressive, its overall impact on Telstra’s e-mail traffic has been “negligible”, he said.

“We didn’t have any major problems with loads on the e-mail servers, and we had no shutdowns of the e-mail system,” he said.

Gray said the Sobig.F worm reached its peak in terms of activity on the Telstra network last Friday. Out of the 16,500 virus-infected e-mail messages reported at the Telstra network firewall, 15,170 were infected by the Sobig.F worm.

This figure was up from 13,300 Sobig.F-infected e-mail messages recorded on the previous day, and represented over 10,000 more than the average 1000 to 2000 viruses which hit the telco’s firewall on a daily basis, he said.

The amount, however, is only a small proportion of the 400,000 to 500,000 e-mails transmitted across Telstra’s network each day, he said.

Gray said Telstra followed its standard antivirus procedures to combat the affect of the worm. Within an hour of being notified about Sobig.F, Telstra’s antivirus firewall software had been updated and was rejecting infected e-mail messages, he said.

Telstra’s antivirus software is provided by vendor Trend Micro.

PC World also asked Optus to comment on the impact the latest Sobig.F variant had upon its e-mail servers and network traffic. The ISP, however, was unable to provide figures on what proportion of its network traffic last week was the result of the virus.

Nevertheless, Optus spokesperson Melissa Favero stated the ISP had not been “significantly affected by the virus” and, as a result, had not sent any specific e-mails to its Internet customers warning them about Sobig.F.

“However, we regularly remind customers about e-mail safety. In this case, the virus is spread only by e-mail, so the standard advice of a) not opening e-mail attachments that you are not expecting and b) using an [up to date] antivirus solution to scan incoming e-mails applies normally,” Favero said.

Likewise, iPrimus consumer technical support manager Liparo Finocchiaro said that although the worm has had an effect on overall e-mail traffic on the Web, it has not had any impact on Primus's network.

To help combat against infected e-mails being sent by its customers, Finocchiaro said the ISP has introduced blocking filters to screen e-mails leaving their network.

Sobig.F’s debut online

The Sobig.F worm is the sixth variant of the Sobig mass mailer virus, which initially hit the Internet earlier this year. The worm is carried in e-mail messages with nondescript subjects such as "Re: Thank you!", "Your details" and "Re: wicked screensaver". The worm code is stored in attached executable files with names such as "your_document.pif," "details.pif" and "movie0045.pif", and propagates itself by skimming addresses from files on the computers it infects and targeting them with virus-tinged messages.

Antivirus vendor Computer Associates’ (CA) Australian development lab reported an 800 per cent increase in the number of customer e-mail submissions during the height of the worm’s impact last week. Of these, 72 per cent were the result of Sobig.F.

CA senior security consultant Daniel Zatz said the vendor’s security e-mail submission figures clearly showed Sobig.F’s enormous impact on users worldwide.

“It’s the biggest virus we’ve probably ever had in terms of the number of submissions received,” he said.

Zatz said the next biggest virus recorded by CA in terms of impact was the Klez.H virus. Despite making its first appearance back in April 2002, Klez.H ranked third highest in the number of submissions received by CA as recently as last week, albeit at a significantly lower rate than Sobig.F.

“It [Klez.H] is still coming in today, and is generally the first or second highest submitted virus each week,” he said.

Zatz said the recent Blaster worm had also caused concern for many of its customers.

“We didn’t get such a significant amount of e-mail submissions, but we had a 400 per cent increase in the amount of tech support calls received in its peak,” he said.

“Mass mailers such as Sobig.F mean the user has to double click on the included attachment and are therefore suspicious of the e-mail,” Zatz said. In comparison, the Blaster worm used a network exploit, eliminating user interaction.

“A lot of people didn’t know they had it.”

Zatz said he would also rate Sobig.F as the highest impact worm seen hitting the Internet, due to the sheer number of people affected by it.

Next Sobig iteration forecast

Although Sobig.F-infected e-mails are still circulating the Internet, the amount is lessening, Telstra’s Gray said.

“There is still significant activity,” he said. “Home PCs are still infected, as a lot of people don’t know about it [the worm] or that they’ve got it. Corporate users seem to be more aware and have updated their antivirus software.

“The pattern is that it will take a couple of weeks for the virus to die down.”

Zatz seconded this comment, saying CA had seen a massive drop in the number of Sobig.F infected e-mail submissions this week.

“We’re getting around a 150 per cent increase on normal rate, which is not a huge increase now [on the average],” he said.

But he warned users hadn’t seen the last of the Sobig worm.

“We will see more variants of Sobig appear in the future – at least one more,” he said.

“Klez.H, for example, was the biggest and still is the most popular form of the Klez virus. In this version, they bundled a second virus in, too.

“Watch this space.”

- Paul Roberts contributed to this report.

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