Note about 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 case, the tool will be able to remove the infection.

What the tool does:

The W32.Klez Removal Tool does the following:

It terminates all processes that are associated with W32.Klez@mm or W32.Elkern.
It deletes the W32.Klez@mm services.
It removes the registry entries that were created by W32.Klez@mm.
It detects all types of W32.Klez@mm and W32.ElKern infections, and repairs files that can be repaired.

Notes:

A file that is 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 the encrypted file is not restored. The W32.ElKern repair removes the viral code from the file. It does not ensure that a file that is repaired from W32.ElKern will run because this virus often corrupts files.

Command-line switches that are 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=	Creates a log file where 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--see notes).
/START	Forces the tool to start scanning immediately.
/EXCLUDE=	Excludes the specified 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 mapped drives scans only the folders that are mapped. This might not include all folders on the remote computer, and this 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 that is infected with W32.Klez@mm may fail if this file is located on the mapped drive. This is because the path to the original encrypted host file is a local path.

For these reasons, you should run the tool on every computer.

To obtain and run 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 that is known to be uninfected).
To check the authenticity of the digital signature, refer to the section The digital signature.
Close all 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, then disable System Restore. Refer to the section System Restore option in Windows Me/XP for additional details. NOTE: If you are running Windows Me/XP, Symantec strongly recommends that you do not skip this step.
Restart the computer in Safe mode (all versions of Windows except Windows NT). For instructions, read the document for your version of Windows. How to start Windows XP in Safe mode. How to start Windows 2000 in Safe mode. How to restart Windows 9x or Windows Me 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.
Restart the computer normally.
Next, you must reinstall NAV. For consumer products such as NAV 2000/2001/2002, follow the instructions in the document How to restore Norton AntiVirus after removing a virus. For Enterprise versions, contact your system administrator.
Run LiveUpdate to make sure that you are using the most current virus definitions, and scan the computer again. If NAV detects any infected files and cannot repair them, then choose to delete the files.
If you are running Windows Me/XP, re-enable System Restore.

NOTE:The removal procedure might be unsuccessful if Windows Me/XP System Restore was not disabled as previously directed because Windows prevents System Restore from being modified by outside programs. Because of this, the removal tool might fail. 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). The instructions for running NAV from the command line and reinstalling NAV are in the removal section of the W32.Klez.E@mm writeup.

When the tool has finished running, you will see a message that indicates whether the computer was infected by variants of W32.Klez@mm and/or variants of W32.ElKern. If an infection was removed, the program displays the following results:

The total number of the scanned files
The number of deleted files
The number of repaired files
The number of viral processes terminated
The number of viral services deleted
The number of registry entries fixed

System Restore option in Windows Me/XP

Windows Me and Windows XP users should temporarily turn off System Restore. This feature, which is enabled by default, is used by Windows Me/XP to restore 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 that you could accidentally restore an infected file, or that online scanners would detect the threat in that location.

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.