Discovered: February 18, 2004
Updated: July 19, 2006 12:00:00 AM
Type: Removal Information
Symantec Security Response has developed a removal tool to clean the infections of the following variants of the Netsky worm:
Note: Misleading Applications, also known as Rogue Security Software, are fake antivirus programs that display fake virus infection alerts in order to trick users into downloading or paying for the application. Two commonly reported fake infections are “Worm.Win32.Netsky” and “Win32.Netsky.Q”.
While similar to the name of the threat in this writeup, these fake detections are not related, and running the removal tool will report that no instances of the threat were found on your computer. For more information about Misleading Applications, see the recent Symantec Report on Rogue Security Software .
What the tool does
The W32.Netsky@mm Removal Tool does the following:
- Terminate the W32.Netsky@mm viral processes.
- Delete the W32.Netsky@mm files
- Delete the registry values that the worms add
- Available command-line switches for this tool
The following switches are designed for use by network administrators:
/HELP, /H, /?
Displays the help message.
Disables the registry repair (We do not recommend using this switch).
Enables the silent mode.
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, FxNetsky.log, in the same folder from which the removal tool was executed.
Scans the mapped network drives (We do not recommend using this switch. See the following Note).
Forces the tool to immediately start scanning.
Excludes the specified [PATH] from scanning (We do not recommend using this switch. See the following Note).
Prevents the scanning of the file system.
Important : Using the /MAPPED switch does not ensure the complete removal of the virus on the remote computer, because:
- The scanning of the mapped drives scans only the mapped folders. This may not include all the folders on the remote computer, which can 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.
The /EXCLUDE switch will only work with one path, not multiple. An alternative is the /NOFILESCAN switch followed by a manual scan with AntiVirus. This will let the tool alter the registry. Then, scan the computer with AntiVirus and with the current virus definitions. You should be able to clean the file system after completing these steps.
The following example command line can be used to exclude a single drive:
"C:\Documents and Settings\user1\Desktop\FxNetsky.exe" /EXCLUDE=M:\ /LOG=c:\FxNetsky.txt
Alternatively, the command line below will skip the scanning of the file system, but will repair the registry modifications. Run a regular scan of the system with the proper exclusions:
"C:\Documents and Settings\user1\Desktop\FxNetsky.exe" /NOFILESCAN /LOG=c:\FxNetsky.txt
Note: The name of the log file can be whatever you select. The name listed is for the sole purpose of this example.
How to download and run the tool
Important: You must have administrative rights to run this tool on Windows NT 4.0, Windows 2000, or Windows XP.
Note for network administrators: For network administrators. If you are running MS Exchange 2000 Server, we recommend that you exclude the M drive from the scan by running the tool from a command line with the Exclude switch. For more information, read the Microsoft knowledge base article, XADM: Do Not Back Up or Scan Exchange 2000 Drive M (Article 298924).
Follow these steps to download and run the tool:
- Download the FxNetsky.exe file from:
- Save the file to a convenient location, such as your downloads folder or the Windows desktop, or removable media known to be uninfected.
- Optional: To check the authenticity of the digital signature, refer to the "Digital signature" section later in this writeup.
Note: If you are sure that you are downloading this tool from the Security Response Web site, you can skip this step. If you are not sure, or are a network administrator and need to authenticate the files before deployment, follow the steps in the "Digital signature" section before proceeding with step 4.
- Close all the running programs before running the tool.
- 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 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 FxNetsky.exe file to start the removal tool.
- Click Start to begin the process, and then allow the tool to run.
Note: If you have any problems when you run the tool, or it does nor appear to remove the threat, restart the computer in Safe mode and run the tool again.
- 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.
Note: The removal procedure may not be successful if Windows Me/XP System Restore is not disabled as previously directed, because Windows prevents outside programs from modifying System Restore.
When the tool has finished running, you will see a message indicating whether W32.Netsky@mm infected the computer. In the case of a removal of the worm, the program displays the following results:
- Total number of scanned files
- Number of deleted files
- Number of repaired files
- Number of terminated viral processes
- Number of fixed registry entries
FxNetsky.exe is digitally signed. Symantec recommends that you use only copies of FxNetsky.exe, which 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 in which you saved the removal tool.
Note: Most of the following steps are done at a command prompt. If you downloaded the removal tool to the Windows desktop, it will be easier if you first move the tool to the root of the C drive. Then save the Chktrust.exe file to the root of C as well.
(Step 3 to assume that both the removal tool and Chktrust.exe are in the root of the C drive.)
- Click Start > Run.
- Type one of the following:
- Click OK.
- In the command window, type the following, pressing Enter after typing each line:
chktrust -i FxNetsky.exe
- You should see one of the following messages, depending on your operating system:
Windows XP SP2:
The Trust Validation Utility window will appear.
Under Publisher, click the Symantec Corporation link. The Digital Signature Details appears.
Verify the contents of the following fields to ensure that the tool is authentic:
Name: Symantec Corporation
Signing Time: Friday, April 04, 2008 4:53:41 AM
All other operating systems:
You should see the following message:
Do you want to install and run "W32.Netsky Removal Tool" signed on 04/04/08 04:53:41 AM PDT and distributed by Symantec Corporation?
The date and time in the digital signature above are based on Pacific time. They will be adjusted your computer's time zone and Regional Options settings.
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, 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 or Run 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 onto your computer, even after you have cleaned the infected files from all the other locations.
Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.
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, see the Microsoft Knowledge Base article, Antivirus Tools Cannot Clean Infected Files in the _Restore Folder, Article ID: Q263455.