MyDoom is the worst virus ever

Switch off your auto-responder. Now!

The prolific MyDoom worm has outpaced Sobig-F to become the fastest spreading virus ever, according to email filtering outfit MessageLabs.

MessageLabs blocked 1.2 million copies of MyDoom (AKA Novarg) in the 24 hours after it first appeared on Monday. At its peak the virus accounted for one in 12 emails.

In comparison, last August's SoBig-F pandemic peaked with one in 17 email messages containing a copy of the virus. MessageLabs blocked one million copies of SoBig-F in the first day of that outbreak.

Just like SoBig-F, much of the huge volume of crap generated by MyDoom is the result of auto-responder messages. As well as replies that someone is out of the office users are getting a stream of accusatory messages from anti-virus gateway products accusing them of sending a virus.

MyDoom spoofs the 'from' field in infectious emails, but AV products are still incapable of recognising this: hence the tide of confusing messages.

These auto-spam messages are stripped of viral attachments but still contribute to the message load on organisations which are otherwise protected against the virus.

We’re all MyDoomed

MyDoom attempts to spread via email and by copying itself to any available shared directories used by Kazaa. Emails have variable subject and attachment names and originate from spoofed email addresses.

Infected attachments have double extensions (e.g. .txt.pif or .htm.zip) in a ploy designed to disguise their hostile payload.

MessageLabs reckons this ploy is a major reason behind the rapid spread of the worm, but there may be additional reasons to consider.

Sneakily, MyDoom avoids sending itself to the email addresses of government departments or the military, in a possible move designed to avoid early detection. (See Symantec advisory here)

The longer a virus can spread without AV vendors noticing it the better the chance it has of reaching critical mass and thereafter wreaking maximum mayhem.

This is, as far as we are aware, the first time that virus writers have used this stealth-spreading approach, which further exposes the shortcomings of the scanner model in fighting rapidly spreading computer viruses.

So what is to be done?

MyDoom is programmed to packet SCO’s web site from infected machines starting February 1 and is programmed to stop spreading on February 12. Business users are advised to filter for Windows executables and zip files in their email. In the home, it's time to update AV signatures yet again. ®

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