New Sober variant becomes the years largest email worm outbreak

F-Secure has been tracking the latest variant of the Sober worm and is now issuing a Radar Level 1 Alert on it. Level 1 is the highest alert level on F-Secure’s 3-step alerting system. Several millions of infected emails have been seen by internet operators over the last hours.

One of the reasons why this email worm seems to be so successful in spreading is that some of the messages it sends are fake warnings from FBI, CIA or from the German Bundeskriminalamt (BKA). Examples of such messages include:

Dear Sir/Madam,
We have logged your IP-address on more than 30 illegal Websites.
Please answer our questions!
The list of questions are attached.
Yours faithfully,
Steven Allison
*** Federal Bureau of Investigation -FBI-

Such emails arrive with an attachment, which will infect the computer once opened.

First Sober was found in October 2003, over two years ago. F-Secure believes all 25 variants of this virus have been written by the same individual, operating from somewhere in Germany. Unlike most of the other widespread viruses nowadays, Sober doesn’t seem to have a clear financial motive behind it.

Some Sober variants have displayed neo-nazi messages, but the latest version of the virus does not do this. However, all Sober variants send German messages to German email addresses and English messages to other addresses.

“The numbers we’re now seeing with Sober.Y are just huge”, comments Mikko Hypponen, Chief Research Officer at F-Secure Corporation. This is the largest email worm outbreak of the year – so far!

More in F-Secure blog at:

Technical information and screenshots of the virus are available at

FBI’s warning on the fake emails at:

F-Secure Anti-Virus can detect and remove the Sober.Y variant.


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