W32.Klez.E@mm

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Discovered: January 17, 2002
Updated: February 13, 2007 11:53:18 AM
Also Known As: W32/Klez.e@MM [McAfee], WORM_KLEZ.E [Trend], Klez.E [F-Secure], W32/Klez-E [Sophos], Win32.Klez.E [CA], I-Worm.Klez.E [AVP]
Type: Worm, Virus
Systems Affected: Windows
CVE References: CVE-2001-0154



Due to a decreased rate of submissions, Symantec Security Response has downgraded the threat level for W32.Klez.E@mm from Category 3 to Category 2 as of July 23, 2002.

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/security/bulletin/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.

Removal tool
Symantec has provided a tool to remove infections of all known variants of W32.Klez and W32.ElKern. Click here to obtain the tool.
This is the easiest way to remove these threats and should be tried first.


Note on W32.Klez.gen@mm detections:
W32.Klez.gen@mm is a generic detection that detects variants of W32.Klez. Computers that are infected with W32.Klez.gen@mm have most likely been exposed to either W32.Klez.E@mm or W32.Klez.H@mm. If your computer is detected as infected with W32.Klez.gen@mm , download and run the tool. In most cases, the tool will be able to remove the infection.





It has been reported that W32.Klez.E@mm may arrive in the following email message promoting a Symantec removal tool. Symantec never sends unsolicited email; the attachment should be deleted.

Subject:  W32.Elkern removal tools

Message:
Symantec give you the W32.Elkern removal  tools. W32.Elkern is a dangerous virus that can infect on Win98/Me/2000/XP.

For more information,please visit http:/ /www.Symantec.com  

Attachment: Install.exe

NOTE: Variations of this message have also been seen purporting to be removal tools for W32.Klez.

For information about how Klez affects a Macintosh computer, read the document Are Macintoshes affected by the Klez virus?

Antivirus Protection Dates

  • Initial Rapid Release version January 17, 2002
  • Latest Rapid Release version January 15, 2018 revision 020
  • Initial Daily Certified version January 17, 2002
  • Latest Daily Certified version January 15, 2018 revision 024
  • Initial Weekly Certified release date January 23, 2002

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Atli Gudmundsson

Discovered: January 17, 2002
Updated: February 13, 2007 11:53:18 AM
Also Known As: W32/Klez.e@MM [McAfee], WORM_KLEZ.E [Trend], Klez.E [F-Secure], W32/Klez-E [Sophos], Win32.Klez.E [CA], I-Worm.Klez.E [AVP]
Type: Worm, Virus
Systems Affected: Windows
CVE References: CVE-2001-0154


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

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

or it creates the registry key

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Wink[random characters]

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:

ANTI-VIR.DAT
CHKLIST.DAT
CHKLIST.MS
CHKLIST.CPS
CHKLIST.TAV
IVB.NTZ
SMARTCHK.MS
SMARTCHK.CPS
AVGQT.DAT
AGUARD.DAT

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.

NOTES:
  • 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 jsmith@anyplace.com, you could receive a message that appears to be from postmaster@anyplace.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

http://www.microsoft.com/technet/security/bulletin/MS01-020.asp

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.

Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

Writeup By: Atli Gudmundsson

Discovered: January 17, 2002
Updated: February 13, 2007 11:53:18 AM
Also Known As: W32/Klez.e@MM [McAfee], WORM_KLEZ.E [Trend], Klez.E [F-Secure], W32/Klez-E [Sophos], Win32.Klez.E [CA], I-Worm.Klez.E [AVP]
Type: Worm, Virus
Systems Affected: Windows
CVE References: CVE-2001-0154


Norton AntiVirus has been able to detect W32.Klez.E@mm since January 17, 2002. If you have current definitions and have a current version of Norton AntiVirus set as recommended (to scan all files), W32.Klez.E@mm will be detected if it attempts to activate. If you simply suspect that the (inactivated) file resides on the computer, run LiveUpdate to make sure that you have current definitions, and then run a full system scan.

If W32.Klez.E@mm has activated, in most cases you will not be able to start Norton AntiVirus. Once this worm has executed, it can be difficult and time consuming to remove. The procedure that you must use to do this varies with the operating system. Please read and follow all instructions for your operating system.

Removal tool

Symantec has provided a tool to remove infections of all known variants of W32.Klez and W32.ElKern. Click here to obtain the tool.
This is the easiest way to remove these threats and should be tried first.

Note on W32.Klez.gen@mm detections:
W32.Klez.gen@mm is a generic detection that detects variants of W32.Klez. Computers that are infected with W32.Klez.gen@mm have most likely been exposed to either W32.Klez.E@mm or W32.Klez.H@mm. If your computer is detected as infected with W32.Klez.gen@mm , download and run the tool. In most cases, the tool will be able to remove the infection.

Manual removal procedure for Windows 95/98/Me

Follow the instructions in the order shown. Do not skip any steps. This procedure has been tested and will work in most cases.

NOTE: Due to the damage that can be done by this worm, and depending on how many times the worm has executed, the process may not work in all cases. If it does not, you may need to obtain the services of a computer consultant.

1. Download virus definitions
Download the definitions using the Intelligent Updater. Save the file to the Windows desktop. This is a necessary first step to make sure that you have current definitions available later in the removal process. Intelligent Updater virus definitions are available at

http://securityresponse.symantec.com/avcenter/defs.download.html

For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, read the document How to update virus definition files using the Intelligent Updater .

2. Restart the computer in Safe mode
You must do this as the first step. For instructions, read the document How to restart Windows 9x or Windows Me in Safe mode .

3. Edit the registry
You must edit the key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Current Version\Run and remove the wink???.exe value after you write down the exact name of the wink file.

CAUTION : We strongly recommend that you back up the system registry before you make any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure that you modify only the keys that are specified. Please see the document How to back up the Windows registry before you proceed.

  1. Click Start, and click Run. The Run dialog box appears.
  2. Type regedit and then click OK. The Registry Editor opens.
  3. Navigate to the following key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
  4. In the right pane, look for the following values:

    Wink[random characters] %System%\Wink[random characters].exe
    WQK %System%\Wqk.exe

  5. Write down the exact file name of the Wink[random characters].exe file
  6. Delete the Wink[random characters] value and the WQK value (if it exists).
  7. Navigate to and expand the following key:

    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services
  8. In the left pane, under the \Services key, look for the following subkey, and delete it if it exists:

    \Wink[random characters]

    NOTE: This probably will not exist on Windows 95/98/Me-based computers, but you should check for it anyway.
  9. Click Registry, and click Exit.

4. Delete the actual Wink[random characters] file
Using Windows Explorer, open the C:\Windows\System folder and locate the Wink[random characters].exe file. (Depending on your system settings, the .exe extension may not be displayed.)

NOTE : If you have Windows installed to a location other than C:\Windows, make the appropriate substitution.

5. Empty the recycle bin
Right-click the Recycle bin on the Windows desktop, and click Empty Recycle Bin.

6. Run the Intelligent Updater
Double-click the file that you downloaded in Step 1. Click Yes or OK if prompted.

7. Restart the computer
Shut down the computer, and turn off the power. Wait 30 seconds, and then restart it. Allow it to start normally. If any files are detected as infected, Quarantine them. Some of the files that you may find are Luall.exe, Rescue32.exe, and Nmain.exe.

8. Scan with Norton AntiVirus (NAV) from a command line
Because some NAV files were damaged by the worm, you must scan from a command line.
  1. Click Start, and click Run.
  2. Type--or copy and paste--the following, and then click OK:

    NAVW32.EXE /L /VISIBLE
  3. Allow the scan to run. Quarantine any additional files that are detected.

9. Restart the computer
Allow it to start normally.

10. Reinstall NAV

NOTE:
If you are using NAV 2002 on Windows XP, this may not be possible on all systems. You can, however, try the following: Open the Control Panel, double-click Administrative Tools, and then double-click Services. In the list, select Windows Installer. Click Action and then click Start.

Follow the instructions in the document How to restore Norton AntiVirus after removing a virus to reinstall NAV.

11. Restart the computer and scan again
  1. Shut down the computer, and turn off the power. Wait 30 seconds and then restart it.

    CAUTION: This step is very important. Reinfection will occur if this is not followed.
  2. Run LiveUpdate and download the most current virus definitions.
  3. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
  4. Run a full system scan. Quarantine any files that are detected as infected by W32.Klez.E@mm or W32.Klez.gen@mm.

Manual removal procedure for Windows 2000/XP

1. Download virus definitions
Download the definitions using the Intelligent Updater. Save the file to the Windows desktop. This is a necessary first step to make sure that you have current definitions available later in the removal process. Intelligent Updater virus definitions are available at

http://securityresponse.symantec.com/avcenter/defs.download.html

For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, read the document How to update virus definition files using the Intelligent Updater .

2. Restart the computer in Safe mode
You must do this as the first step. All Windows 32-bit operating systems except Windows NT can be restarted in Safe mode. Read the document for your operating system.
3. Edit the registry
You must edit the key HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services and remove the wink[random characters] .exe subkey after you write down the exact name of the wink file.

CAUTION : We strongly recommend that you back up the system registry before you make any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure that you modify only the keys that are specified. Please see the document How to back up the Windows registry before you proceed.
  1. Click Start, and click Run. The Run dialog box appears.
  2. Type regedit and then click OK. The Registry Editor opens.
  3. Navigate to the following key:

    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services
  4. In the left pane, under the \Services key, look for the following subkey:

    \Wink[random characters]

  5. Write down the exact file name of the Wink[random characters].exe file
  6. Delete the Wink[random characters] subkey.
  7. Navigate to the following key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
  8. In the right pane, look for the following values, and delete them if they exist:

    Wink[random characters] %System%\Wink[random characters].exe
    WQK %System%\Wqk.exe

    NOTE: They probably will not exist on Windows 2000/XP-based computers, but you should check for them anyway.
  9. Click Registry, and click Exit.

4. Configure Windows to show all files
Do not skip this step.
  1. Start Windows Explorer.
  2. Click the Tools menu, and click "Folder options."
  3. Click the View tab.
  4. Uncheck "Hide file extensions for known file types."
  5. Uncheck "Hide protected operating system files," and under the "Hidden files" folder, click "Show hidden files and folders."
  6. Click Apply, and then click OK.

5. Delete the actual Wink[random characters] file
Using Windows Explorer, open the C:\Winnt\System folder and locate the Wink[random characters].exe file. (Depending on your system settings, the .exe extension may not be displayed.)

NOTE : If you have Windows installed to a location other than C:\Windows, make the appropriate substitution.

6. Empty the recycle bin
Right-click the Recycle bin on the Windows desktop, and click Empty Recycle Bin.

7. Run the Intelligent Updater
Double-click the file that you downloaded in Step 1. Click Yes or OK if you are prompted.

8. Restart the computer
Shut down the computer, and turn off the power. Wait 30 seconds, and then restart it.

CAUTION: This step is very important. Reinfection will occur if this is not followed.

Allow the computer to start normally. If any files are detected as infected by W32.Klez.E@mm or W32.Klez.gen@mm, Quarantine them. Some of the files that you may find are Luall.exe, Rescue32.exe, and Nmain.exe.

9. Scan with Norton AntiVirus (NAV) from a command line
Because some NAV files were damaged by the worm, you must scan from the command line.

NOTE: These instructions are only for consumer versions of NAV. The file Navw32.exe is not part of Enterprise versions of NAV such as NAVCE. The NAVCE command-line scanner, Vpscan.exe, will not remove the worm.
  1. Click Start, and click Run.
  2. Type--or copy and paste--the following, and then click OK:

    NAVW32.EXE /L /VISIBLE
  3. Allow the scan to run. Quarantine any additional files that are detected.

10. Reinstall NAV

NOTE:
If you are using NAV 2002 on Windows XP, this may not be possible on all systems. You can, however, try the following: Open the Control Panel, double-click Administrative Tools, and then double-click Services. In the list, select Windows Installer. Click Action, and then click Start.

Follow the instructions in the document How to restore Norton AntiVirus after removing a virus to reinstall NAV.

11. Restart the computer and scan again
  1. Shut down the computer, and turn off the power. Wait 30 seconds and then restart it.

    CAUTION: This step is very important. Reinfection will occur if this is not followed.
  2. Run LiveUpdate and download the most current virus definitions.
  3. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
  4. Run a full system scan. Quarantine any files that are detected as infected by W32.Klez.H@mm or W32.Klez.gen@mm.


Writeup By: Atli Gudmundsson