New email worm breaks infection records

A new computer virus that spreads using email messages is breaking records for new infections set by the last major email worm, Sobig.F, according to leading antivirus software companies and email security firms.

A new computer virus that spreads using email messages is breaking records for new infections set by the last major email worm, Sobig.F, according to leading antivirus software companies and email security firms.

Infected email messages carrying the Mydoom virus, also known as "Shimgapi" and "Novarg," have been intercepted from over 142 countries and now account for one in every 12 email messages, according to Mark Sunner, chief technology officer at email security company MessageLabs

That surpasses the Sobig.F virus record, which appeared last August and, at its peak, was found in one of every 17 messages intercepted by MessageLabs, he says.

Since first detecting the new virus at 1pm GMT on Monday (2am Tuesday NZ time), MessageLabs intercepted almost 1 million infected email messages carrying the virus, Sunner says.

The virus has "followed the sun," hitting hard in the US and Canada late on Monda (US time), then working its way through Asia and Europe on Tuesday, he says.

F-Secure of Helsinki estimates that around 100,000 computers have been infected with Mydoom so far, says Mikko Hyppönen, manager of antivirus research at F-Secure.

Antivirus experts expect another large wave of infections in the US and Canada on Tuesday morning, as workers who missed the virus late Monday return to their desks, he says.

The worm arrives as a file attachment in an email with a variety of senders and subjects, such as "Hello," and "test." The message body is often technical sounding, imitating the look and feel of an automatically generated message from an email server, Sunner says.

For example, some email messages tell recipients that "the message contains unicode characters and has been sent as a binary attachment," or "The message cannot be represented in 7-bit ASCII encoding and has been sent as a binary attachment."

Users who click on the attachment, which uses a variety of file extensions such as ZIP, SCR, EXE and PIF, are infected with the virus.

The technical pitch is a new twist on so-called "social engineering" techniques used by virus writers to trick users into opening malicious file attachments. Mydoom's authors may have been counting on the fact that people trust the authenticity of computer generated messages more than those purporting to come from other humans, Sunner says.

Mimicking the language of a computer-generated administrative message may have also helped Mydoom spread within large corporations, where employees are used to receiving such messages from administrative systems, according to David Perry, public education director at antivirus company Trend Micro.

Trend Micro saw evidence yesterday of infections from 12 of the Fortune 100 companies, he says.

Once inside such companies, Mydoom could use the enormous bandwidth of those corporate networks and huge email address books as a "springboard" to the rest of the internet, Perry says.

While Mydoom has shattered Sobig.F records, in many ways the two viruses are the same, antivirus experts agreed.

Both viruses scan infected computers for email addresses that are then targeted by infected email. Also, both Sobig.F and Mydoom are small and contain highly efficient SMTP (Simple Mail Transfer Protocol) engines for sending out copies of themselves. The efficiency of their mail engines means that even a small number of infections can generate a massive amount of email traffic, Hyppönen said.

Finally, both Sobig.F and Mydoom contain a Trojan horse program that gives remote attackers full control of the infected system, he says.

In the case of Sobig.F, experts theorized that the virus was being used to assemble "zombie" networks of machines for distributing unsolicited commercial ("spam") email. A similar motive may be behind Mydoom, though the virus writer's intentions are not yet clear, says Perry.

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