Antivirus software companies have warned of another
variant of the Sober e-mail worm, which appeared on the internet
masquerading as a Microsoft software update.
Sober.D is the latest version of a worm that first appeared in
October. The worm poses as a software patch which will remove the
MyDoom virus from infected Windows systems, said antivirus company
F-Secure.
F-Secure first detected the worm variant in Germany and rated
the virus a "Level 2" threat, indicating large infections.
Like its predecessors, Sober.D spreads by skimming e-mail
addresses from victims' computers, then mailing copies of itself to
those addresses.
Sober.D also adapts its message for German speaking audiences,
inserts a German-language version of its pitch message into e-mail
addresses belonging to German domains, such as those ending in .de,
F-Secure said.
Copies of the Sober.D worm arrive in e-mail messages with the
subject "Microsoft Alert: Please Read!" or "Microsoft Alarm: Bitte
Lesen!".
The worm file is embedded in file attachments with the EXE or
Zip file extension and names such as "Patch", "MS-Security" and
"UpDate", F-Secure said.
Once the worm file has been opened, the virus places a copy of
itself on the infected machine's hard drive and modifies the
Windows configuration so that the worm file is launched each time
Windows starts.
When run, the worm mimics a legitimate software patch,
displaying a pop-up message indicating that the "patch has been
successfully installed".
For machines that are already infected, the worm displays a
message saying that the "patch does not need to be installed on
this system".
It is common for worm authors to dress up their creations as
software updates from Microsoft.
Microsoft has said that it never distributes software updates
using e-mail and has published guidelines for identifying
legitimate e-mail from the company.
(
www.microsoft.com/security/antivirus/authenticate_mail.asp)
Antivirus companies have recommended that customers update their
software as soon as possible to prevent Sober.D infection.
Paul Roberts writes for IDG News Service