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W32.Klez Removal Tool

Updated:
July 19, 2006 12:00:00 AM
Type:
Removal Information
Symantec offers a tool to remove infections of all known variants of W32.Klez@mm, as well as all known variants of W32.Elkern.

To view an online demonstration on how to download and run this and several other tools, click here.

About W32.Klez.gen@mm detections
W32.Klez.gen@mm is a generic detection that detects variants of W32.Klez. Computers 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.

What the tool does
The W32.Klez Removal Tool:
Terminates all the processes associated with W32.Klez@mm or W32.Elkern.
Deletes the services of W32.Klez@mm.
Removes the registry entries created by W32.Klez@mm.
Detects all types of W32.Klez@mm and W32.ElKern infections and repairs the repairable files.
Innoculates the W32.Elkern.4926 repaired files to prevent re-infection.

NOTES
A file infected with W32.Klez.E@mm or W32.Klez.H@mm includes a link to the encrypted host file. If the encrypted file does not exist at that link, the tool deletes the infected file, because it is not repairable, and thus, the encrypted file is not restored.
The W32.ElKern repair removes the viral code from the infected file. It does not ensure that a file repaired from a W32.ElKern attack will run, as this virus often corrupts files.

Command-line switches available for this tool

Switch Description
/HELP, /H, /? Displays the help message.
/NOFIXREG Disables registry repair (the use of this switch is not recommended).
/SILENT, /S Enables silent mode.
/LOG= [PATH NAME] Creates a log file where [PATH NAME] is the location in which to store the tool's output. By default, this switch creates the log file FixKlez.log in the same folder from which the removal tool was executed.
/MAPPED Scans mapped network drives (the use of this switch is not recommended—refer to the following Note).
/START Forces the tool to immediately start scanning.
/EXCLUDE= [PATH] Excludes the specified [PATH] from scanning (the use of this switch is not recommended).

NOTE: The use of the /MAPPED switch does not ensure the complete removal of the virus on the remote computer, because:
The scanning of the mapped drives scans the mapped folders only. This may not include all the folders on the remote computer, which can to lead to missed detections.
If a viral file is detected on the mapped drive, the removal will fail if a program on the remote computer is using this file.
The repair of a file infected with W32.Klez@mm may fail if this file is located on the mapped drive, because the path to the original encrypted host file is a local path.
For these reasons, you should run the tool on every computer.

Obtaining and running the tool

NOTE: You must have administrative rights to run this tool on Windows NT 4.0, Windows 2000, or Windows XP.

Download the FixKlez.com file from http://securityresponse.symantec.com/avcenter/FixKlez.com.
Save the file to a convenient location, such as your download folder or the Windows desktop (or, if possible, removable media known to be uninfected).
To check the authenticity of the digital signature, refer to the "Digital signature" section later in this writeup.
Close all the programs.
If you are on a network, or if you have a full-time connection to the Internet, disconnect the computer from the network and the Internet.
If you are running Windows Me or Windows XP, disable System Restore. Refer to the "System Restore option in Windows Me/XP" section, later in this writeup, for additional details.

NOTE: If you are running Windows Me/XP, Symantec strongly recommends that you do not skip this step.

Shut down the computer and turn off the power. Wait 30 seconds. Do not skip this step.
Restart the computer in Safe mode. All the Windows 32-bit operating systems, except Windows NT, can be restarted in Safe mode. For instructions on how to do this, read the document, "How to start the computer in Safe Mode."
Double-click the FixKlez.com file to start the removal tool.
Click Start to begin the process and allow the tool to run.
Normally restart the computer.
Next, if you are using a Symantec antivirus product, re-install it.
For consumer products such as Norton AntiVirus 2000/2001/2002/2003, follow the instructions in the document, "How to restore Norton AntiVirus after removing a virus."
For Enterprise products, contact your system administrator.
Run LiveUpdate to make sure that you are using the most current virus definitions, and then rescan the computer. If your Symantec antivirus product detects any infected files and cannot repair them, choose to delete the files.
If you are running Windows Me/XP, re-enable System Restore.

NOTE: The removal procedure may not be successful if Windows Me/XP System Restore was not disabled as previously directed, as Windows prevents System Restore from being modified by outside programs. If W32.Klez.gen@mm was activated before you ran the removal tool, in most cases you will not be able to start Norton AntiVirus (NAV). Refer to the "Removal" section of the W32.Klez.E@mm writeup for instructions on running NAV from the command line and re-installing NAV.

When the tool has finished running, you will see a message indicating whether variants of W32.Klez@mm and/or variants of W32.ElKern infected the computer. If an infection was removed, the program displays the following results:
Total number of the scanned files
Number of deleted files
Number of repaired files
Number of terminated viral processes
Number of deleted viral services
Number of fixed registry entries

Digital signature
FixKlez.com is digitally signed. Symantec recommends that you use only copies of FixKlez.com downloaded directly from the Symantec Security Response Web site. To verify the authenticity of the digital signature, follow these steps:
Go to http://www.wmsoftware.com/free.htm.
Download and save the Chktrust.exe file into the same folder in which you saved FixKlez.com (for example, the C:\Downloads folder).
Depending on your version of Windows, do one of the following:
Click Start, point to Programs, and then click MS-DOS Prompt.
Click Start, point to Programs, click Accessories, and then click Command Prompt.
Change to the folder that contains FixKlez.com and Chktrust.exe, and then type:

chktrust -i FixKlez.com

For example, if the file exists in the C:\Downloads folder, enter the following commands:

cdcd downloads
chktrust -i FixKlez.com

Press Enter after you type each command. If the digital signature is valid, you will see the following:

"Do you want to install and run "W32.Klez Fix Tool" signed on 9/10/2002 7:11PM and distributed by Symantec Corporation?"

NOTES
The date and time that appear in this dialog box will be adjusted to your time zone if your computer is not set to the Pacific time zone.
If you are using Daylight Saving Time, the time that appears will be exactly one hour earlier.
If this dialog box does not appear, there are two possible reasons:
The tool is not from Symantec: Unless you are sure that the tool is legitimate and that you downloaded it from the legitimate Symantec Web site, you should not run it.
The tool is from Symantec and is legitimate; however, your operating System was previously instructed to always trust content from Symantec. For information on this and on how to view the confirmation dialog again, read the document, "How to restore the Publisher Authenticity confirmation dialog box."
Click Yes to close the dialog box.
Type exit, and then press Enter to close the MS-DOS session.

System Restore option in Windows Me/XP
Windows Me and Windows XP users should temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. When a computer is infected with a virus, worm, or Trojan, it is possible that the virus, worm, or Trojan could be backed up by System Restore. By default, Windows prevents System Restore from being modified by other programs. As a result, there is the possibility of accidentally restoring an infected file, or online scanners could detect the threat in that particular location. For instructions on how to turn off System Restore, read your Windows documentation or one of the following articles:
"How to disable or enable Windows Me System Restore"
"How to disable or enable Windows XP System Restore"

For additional information and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Anti-Virus Tools Cannot Clean Infected Files in the _Restore Folder," Article ID: Q263455.

Running the tool from a floppy disk
Insert the floppy disk, containing the FixKlez.com file, into the floppy disk drive.
Click Start, and then click Run.
Type the following:

a:\fixklez.com

and then click OK

NOTES
There are no spaces in the command a:\fixklez.com
If you are running Windows Me and System Restore remains enabled, you will see a warning message. You can choose to run the removal tool with the System Restore option enabled, or to exit the removal tool.

Click Start to begin the process, and then allow the tool to run.
If you are running Windows Me, then re-enable System Restore.

NOTE: If you are using Norton AntiVirus (NAV) 2000/2001/2002, in most cases, after you remove the virus you must uninstall and reinstall NAV. For instructions on how to do this, read the document, "How to restore Norton AntiVirus after removing W32.Goner.A@mm or W32.Klez.gen@mm."
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