W32.Gaobot.UJ Removal Tool

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Discovered: April 01, 2004
Updated: December 11, 2005 12:00:00 AM
Type: Removal Information

Symantec Security Response has developed a removal tool to clean the infections of:


What the tool does

The W32.Gaobot.UJ Removal Tool does the following:
Terminates the W32.Gaobot.UJ viral processes and services.
Deletes the W32.Gaobot.UJ files.
Deletes the dropped files.
Deletes the registry values that the worm added.

What the tool does not do

This tool does not restore the hosts file if it has been modified. Please see Step 6 of the Removal Instructions for W32.Gaobot.UJ to correct this modification.

Command-line switches available with this tool

Switch Description
/HELP, /H, /? Displays the help message.
/NOFIXREG Disables the registry repair. (We do not recommend using this switch.)
/SILENT, /S Enables the 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, FxGaoUJ.log, within the same folder from which the removal tool was executed.
/MAPPED Scans the mapped network drives. (We do not recommend using this switch. Refer to the Notes below.)
/START Forces the tool to immediately start scanning.
/EXCLUDE=[PATH] Excludes the specified [PATH] from scanning. (We do not recommend using this switch.)
/NOFILESCAN Prevents scanning of the file system.

Note: Using the /MAPPED switch does not ensure the complete removal of the virus on the remote computer, because:
Scanning the mapped drives scans the mapped folders only. This action may not include all the folders on the remote computer, leading 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.

For these reasons, run the tool on every computer.

Obtaining and running the tool

Note: You need administrative rights to run this tool on Windows NT 4.0, Windows 2000, or Windows XP.

Download the FxGaoUJ.exe file from: http://securityresponse.symantec.com/avcenter/FxGaobotUJ.exe
Save the file to a convenient location, such as your downloads folder or the Windows Desktop (or removable media known to be uninfected, if possible).
To check the authenticity of the digital signature, refer to the section, "Digital signature."
Close all the running programs.
If you are on a network or 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 XP, then disable System Restore. Refer to the section, "System Restore option in Windows Me/XP," for additional details.

CAUTION: If you are running Windows Me/XP, we strongly recommend that you do not skip this step. The removal procedure may be unsuccessful if Windows Me/XP System Restore is not disabled, because Windows prevents outside programs from modifying System Restore.

Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.
For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, How to start the computer in Safe Mode.
For Windows NT 4 users, restart the computer in VGA mode.

Double-click the FxGaoUJ.exe file to start the removal tool.
Click Start to begin the process, and then allow the tool to run.
Restart the computer.
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.

When the tool has finished running, you will see a message indicating whether W32.Gaobot.UJ infected the computer. In the case of a worm removal, the program displays the following results:
Total number of scanned files
Number of deleted files
Number of terminated viral processes
Number of fixed registry entries
Stopped and deleted viral processes and services

Digital signature
FxGaoUJ.exe is digitally signed. Symantec recommends that you only use copies of FxGaoUJ.exe that have been directly downloaded from the Symantec Security Response Web site. To check the authenticity of the digital signature, follow these steps:
Go to http://www.wmsoftware.com/free.htm.
Download and save the Chktrust.exe file to the same folder where you saved FxGaoUJ.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 where FxGaoUJ.exe and Chktrust.exe are stored, and then type:

chktrust -i FxGaoUJ.exe

For example, if you saved the file to the C:\Downloads folder, you would enter the following commands:

cdcd downloads
chktrust -i FxGaoUJ.exe

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

Do you want to install and run "W32.GaoUJ Removal Tool" signed on 04/01/2004 19:04 and distributed by Symantec Corporation?

The date and time displayed in this dialog box will be adjusted to your time zone.
If you are using Daylight Saving time, the displayed time 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, do 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.

System Restore option in Windows Me/XP
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 virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows 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 of restoring an infected file on 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:
How to disable or enable Windows Me System Restore
How to turn off or turn on Windows XP System Restore

For additional information and an alternative to disabling Windows Me System Restore, read the Microsoft Knowledge Base article, Antivirus Tools Cannot Clean Infected Files in the Restore Folder (Article ID: Q263455).

How to run the tool from a floppy disk
Insert the floppy disk, which contains the FxGaoUJ.exe file, in the floppy disk drive.
Click Start, and then click Run.
Type the following:


and then click OK.

There are no spaces in the command, a:\FxGaoUJ.exe.
If you are using Windows Me/XP 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 exit the removal tool.

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