W32.Welchia.Worm Removal Tool
|Discovered on: August 18, 2003|
|Last Updated on: August 19, 2003 02:58:49 PM GDT|
Symantec Security Response has developed a removal tool to clean infections of W32.Welchia.Worm.
What the tool does
The W32.Welchia.Worm Removal Tool does the following:
Available command-line switches for this tool
- Terminates the W32.Welchia.Worm viral processes.
- Deletes the W32.Welchia.Worm files.
- Deletes the registry values that W32.Welchia.Worm added.
- Deletes the services created by W32.Welchia.Worm.
Using 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 mapped folders. 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 uses this file.
Therefore, you should run the tool on every computer.Obtaining and running the tool
You must have administrative rights to run this tool on Windows NT 4.0, Windows 2000, or Windows XP.
- Download the FixWelch.exe file from: http://www.symantec.com/avcenter/FixWelch.exe.
- Save the file to a convenient location, such as your downloads folder or the Windows desktop (or removable media known
to be uninfected).
- To check the authenticity of the digital signature, refer to the "Digital signature" section later in this writeup.
- If you are running Windows Me or XP, then disable System Restore. Refer to the "System Restore option in Windows Me/XP"
section later in this writeup for further details.
Caution: If you are running Windows Me/XP, we strongly
recommend that you do not skip this step.
- Double-click the FixWelch.exe file to start the removal tool.
- Click Start to begin the process, and then allow the tool to run.
- Restart the computer.
- Run the removal tool again to ensure that the system is clean.
- If you are running Windows Me/XP, then re-enable System Restore.
- Run LiveUpdate to make sure that you are using the most current virus definitions.
: The removal
procedure may not be successful if Windows Me/XP System Restore is not disabled as previously directed, because Windows prevents
System Restore from being modified by outside programs.
When the tool has finished running, you will see a message
indicating whether W32.Welchia.Worm infected the computer. In the case of a removal of the worm, the program displays the
- Total number of the scanned files.
- Number of deleted files.
- Number of terminated viral processes.
- Number of fixed registry entries.
FixWelch.exe is digitally signed. Symantec
recommends that you only use copies of FixWelch.exe, which have been directly downloaded from the Symantec Security Response
Web site. To check the authenticity of the digital signature, follow these steps:
System Restore option in Windows
- Go to http://www.wmsoftware.com/free.htm.
- Download and save the chktrust.exe file to the same folder in which you saved FixWelch.exe (for example, C:\Downloads).
- Depending on your operating system, 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 in which FixWelch.exe and Chktrust.exe are stored, and then type: chktrust -i FixWelch.exe.
example, if you saved the file to the C:\Downloads folder, you would enter the following commands:
Press Enter after typing each command. If the digital signature is valid, you will see the following:
you want to install and run "W32.Welchia Removal Tool" signed on 8/19/2003 14:26 PM GMT
and distributed by Symantec Corporation?"
- The date and time displayed 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 displayed 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. (This will close the MS-DOS session.)
Users of Windows Me and Windows XP 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. If a computer becomes infected
with a virus, worm, or Trojan, it is possible that System Restore backed up the virus, worm, or Trojan on the computer.
prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools
cannot remove threats in the System Restore folder. As a result, System Restore has the potential to restore an infected file
onto your computer even after you have cleaned the infected files from all the other locations.
Also, in some cases,
online scanners may detect a threat in the System Restore folder even though you scanned your computer with an antivirus program
and did not find any infected files.
For instructions on how to turn off System Restore, read your Windows documentation,
or one of the following articles:
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.
- August 19, 2003. Posted version 1.0.1.