W32/Klez-G

Please follow the instructions for disinfecting PE executables.

Please read the instructions for removing the W32/ElKern-C and W32/Klez-H viruses.

Please note: Some customers have received this virus as an attachment to an email claiming to contain disinfection tools from Sophos for the W32/ElKern virus (the email calls it "W32.Elkern").

We can confirm that the infected file does not originate from Sophos and we recommend users do not open/launch unsolicited executable attachments.

W32/Klez-G is a Win32 worm that carries a compressed copy of the W32/ElKern-B virus, which it drops and executes when the worm is run.

This worm searches for email address entries in the Windows address book and in files found on local and network hard drives. W32/Klez-G uses its own mailing routine.

The email will have the following characteristics:

Subject line: either random or chosen from the list

How are you
Let's be friends
Darling
Don't drink too much
Your password
Honey
Some questions
Please try again
Welcome to my hometown
the Garden of Eden
introduction on ADSL
Meeting notice
Questionnaire
Congratulations
Sos!
japanese girl VS playboy
Look,my beautiful girl friend
Eager to see you
Spice girls' vocal concert
Japanese lass' sexy pictures

Message text: Message text is randomly composed by the worm but the message can also be without a text.

Attached file: Randomly named with extension .PIF, .SCR, .EXE or .BAT.

The sender address which appears in the message "From:" field is chosen either from files on the local hard drive or from a list inside the virus.

Because the worm uses its own SMTP engine, the message may appear to come from any email address. Some of the messages will have a "From:" field and message text which imply that the message was sent by a major anti-virus vendor.

W32/Klez-G attempts to disable several anti-virus products and delete some anti-virus related files.

The worm attempts to exploit a MIME vulnerability in some versions of Microsoft Outlook, Microsoft Outlook Express, and Internet Explorer to allow the executable file to run automatically without the user double-clicking on the attachment. Microsoft has issued a patch which secures against this vulnerability which can be downloaded from http://www.microsoft.com/technet/security/bulletin/MS01-027.asp.
(This patch fixes a number of vulnerabilities in Microsoft's software, including the one exploited by this worm.)

W32/Klez-G may also spread to remote shares on other machines using random filenames.

It copies itself to the Windows System directory with a random filename. The worm will set the registry key

HKLM\Software\Microsoft\Windows\CurrentVersion\Run\

to point to the worm file, so that the file is run on Windows startup.

Note: Due to a generic detection technique used to detect W32/Klez-G this virus name will also be reported if the most prevalent variant W32/Klez-H is encountered.