For those who might not know...
W32.Klez.E@mm is similar to W32.Klez.A@mm. It is a mass-mailing email worm that also attempts to copy itself to network shares. The worm uses random subject lines, message bodies, and attachment file names.
The worm exploits a vulnerability in Microsoft Outlook and Outlook Express in an attempt to execute itself when you open or even preview the message in which it is contained. Information and a patch for the vulnerability are available at http://www.microsoft.com/technet/se..*****MS01-020.asp
The worm overwrites files and creates hidden copies of the originals. In addition, the worm drops the virus W32.Elkern.3587, which is similar to W32.ElKern.3326
The worm attempts to disable some common antivirus products and has a payload which fills files with all zeroes.
When the worm is executed, it copies itself to %System%\Wink[random characters].exe.
NOTE: %System% is a variable. The worm locates the Windows System folder (by default this is C:\Windows\System or C:\Winnt\System32) and copies itself to that location.
It adds the value
Wink[random characters] %System%\Wink[random characters].exe
to the registry key
or it creates the registry key
and inserts a value in that subkey so that the worm is executed when you start Windows.
The worm attempts to disable on-access virus scanners and some previously distributed worms (such as W32.Nimda and CodeRed) by stopping any active processes. The worm removes the startup registry keys used by antivirus products and deletes checksum database files including:
The worm copies itself to local, mapped, and network drives as:
A random file name with a double extension. For example, filename.txt.exe.
A .rar archive with a double extension. For example, filename.txt.rar.
In addition, the worm searches the Windows address book, the ICQ database, and local files (such as .html and text files) for email addresses. The worm sends an email message to these addresses with itself as an attachment. The worm contains its own SMTP engine and attempts to guess at available SMTP servers.
The subject line, message bodies, and attachment file names are random. The from address is randomly chosen from email addresses that the worm finds on the infected computer.
Because this worm does use a randomly chosen address that it finds on an infected computer as the "From:" address, numerous cases have been reported in which users of uninfected computers receive complaints that they have sent an infected message to someone else.
For example, Linda Anderson is using a computer that is infected with W32.Klez.E@mm; Linda is not using a antivirus program or does not have current virus definitions. When W32.Klez.E@mm performs its emailing routine, it finds the email address of Harold Logan. It inserts Harold's email address into the "From:" line of an infected email that it then sends to Janet Bishop. Janet then contacts Harold and complains that he sent her infected email, but when Harold scans his computer, Norton AntiVirus does not find anything--as would be expected--because his computer is not infected.
If you are using a current version of Norton AntiVirus, have the most recent virus definitions, and a full system scan with Norton AntiVirus set to scan all files does not find anything, you can be confident that your computer is not infected with this worm.
There have been several reports that, in some cases, if you receive a message that the virus has sent using its own SMTP engine, the message appears to be a "postmaster bounce message" from your own domain. For example, if your email address is firstname.lastname@example.org
, you could receive a message that appears to be from email@example.com
, indicating that you attempted to send email and the attempt failed. If this is the false message that is sent by the virus, the attachment includes the virus itself. Of course, such attachments should not be opened.
If the message is opened in an unpatched version of Microsoft Outlook or Outlook Express, the attachment may be automatically executed. Information about this vulnerability and a patch are available at
The worm also infects executables by creating a hidden copy of the original host file and then overwriting the original file with itself. The hidden copy is encrypted, but contains no viral data. The name of the hidden file is the same as the original file, but with a random extension.
The worm also drops the virus W32.Elkern.3587 as the file %System%\wqk.exe and executes it.
Finally, the worm has a payload. On the 6th of every odd numbered month (except January or July), the worm attempts to overwrite with zeroes files that have the extensions .txt, .htm, .html, .wab, .doc, .xls, .jpg, .cpp, .c, .pas, .mpg, .mpeg, .bak, or .mp3. If the month is January or July, this payload attempts to overwrite all files with zeroes, not just those with the aforementioned extensions.