Discovered: August 17, 2006
Updated: February 01, 2007 5:06:08 PM
Also Known As: W32/Narcha-C [Sophos]
Type: Worm
Infection Length: Varies (24 kilobytes to 27 kilobytes + random appended data of up to 15 kilobytes)
Systems Affected: Windows

W32.Narcha is a worm that copies itself to mapped drives and folders that are used by file-sharing applications.

Antivirus Protection Dates

  • Initial Rapid Release version August 17, 2006
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version August 17, 2006
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date August 23, 2006

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Paul Mangan

Discovered: August 17, 2006
Updated: February 01, 2007 5:06:08 PM
Also Known As: W32/Narcha-C [Sophos]
Type: Worm
Infection Length: Varies (24 kilobytes to 27 kilobytes + random appended data of up to 15 kilobytes)
Systems Affected: Windows

When the worm executes, it copies itself to the following locations:

  • %SystemDrive%\Documents and Settings\All Users\Application Data\Microsoft\Internet Explorer\Quick Launch\[COMPUTER NAME].[exe/pif/com/scr]
  • %Temp%\[COMPUTER NAME].[exe/pif/com/scr]
  • %UserProfile%\Start Menu\Programs\Startup\[COMPUTER NAME].[exe/pif/com/scr]
  • %SystemDrive%\Documents and Settings\All Users\Start Menu\Programs\Startup\[COMPUTER NAME].[exe/pif/com/scr]
  • %UserProfile%\Application Data\Microsoft\Internet Explorer\Quick Launch\[COMPUTER NAME].[exe/pif/com/scr]
  • %System%\SVCH0ST.EXE
  • %SystemDrive%\[COMPUTER NAME].[exe/pif/com/scr]

The worm then copies itself to mapped drives as one of the following files:
  • Backup Folder.exe
  • Fine Pictures.exe
  • Office Documents.exe
  • Private Pictures.exe
  • Pictures.exe
  • Music Folder.exe
  • eBooks.exe
  • Shared Network Folder.exe
  • My Documents.exe
  • Microsoft Common Shared Files.exe
  • Funny Jokes.exe
  • New Folder.exe
  • Text Files.exe
  • WinAmp Files.exe
  • PowerPoint Documents.exe
  • Project Report(s).exe
  • Unread Emails.exe
  • Picture Collection.exe
  • Wallpapers.scr
  • Received Pictures.exe
  • Downloads.exe
  • Briefcase Documets.exe
  • Chernobyl April 26.exe
  • .exe
  • Folder.exe
  • Desktop.exe
  • Important Letters.exe
  • Shortcut to Shared Folder.pif
  • Shared Documets.exe
  • README.exe
  • SubFolders
  • My Shared Documents.exe
  • Common Files.exe
  • Zipped Folder.exe
  • Wma Files.exe
  • Screensaver Collection.scr

The worm also copies itself to folders containing one of the following substrings:
  • shared
  • document
  • folder
  • music
  • picture

It copies itself to the above folders using one of the following file names:
  • Hot+Fun+BeachBabes Flash Game.exe
  • software\microsoft\windows\currentversion\run
  • \SVCH0ST.exe
  • Microsoft Agent
  • W32.TOXO999
  • Saddams Birthday Video [Flash Movie].exe
  • Serial Key Generator + Patch.exe
  • Adult PACMAN 2 Game [FULL].exe
  • WinRAR Working Patch.exe
  • Women's Tennis Goes Nude [Flash Game].exe
  • Funny Screensavers.scr
  • 3000+ Sexy Girl's Full Site Access USERNAME,PASSOWRD Generator For Free Hot+sex+nude+Boobs+XXX+Erotica+rape+Blond+HARDCORE.Asp.html.exe
  • Google Earth Pro FULL Regestry Patch.exe
  • Folder Locker Setup 2.01 [FULL Patched].exe
  • Winzip 10.00 + WinRAR 5.1 + WinAce 7.00 ALL in ONE Ultimate Patch [From CoRe].exe
  • Macfee + Norton AntiVirus GoLive Regestry Patch.reg.exe
  • Internet Explorer + Mozilla Firefox Parental Adult Passsword Filter Remover .exe
  • Funny Folder.scr
  • Hottest Blog on Pornography Sex Icons [Advisory]
  • Blog on LSD,Marijuana,Hashish,Drugs Making.html.exe
  • Nokia,Samsung,Sony Mobile Hacks Secret unlock codes CHEATBOOK [FULL].msi.exe
  • DivX JetAudio All Version Working Patch.exe
  • Britney,Madonna,Pink,girls, Porn Exposed+hot+sex+pictures.pif
  • MSN Hotmail Password
  • Yahoo Msn Password
  • Basic emails hacking tricks.Documents.pif
  • Windows XP Secrets [README Document].com
  • Shortcuts to XXX FULL PASS SITES.pif
  • Wallpaper Collection.exe
  • Default folder .exe
  • Common Wallpapers.exe
  • ScreenSaver.exe
  • More Information.exe
  • Updated Downloads.exe
  • Shared Files.exe
  • RegDelete
  • UPDATE.exe
  • Shortcut to Music Folder.pif
  • Explorer.Zip.scr
  • .com
  • Shared Pictures.exe
  • Shortcut to Private Folder.pif
  • Shortcut to Shared Items.pif
  • Macromedia Collection.exe
  • Shortcut to Flash Games.pif
  • Downloaded eBooks.exe
Next, the worm creates the following registry entry so that it executes whenever Windows starts:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run\"Microsoft Agent" = "%System%\SVCH0ST.exe"

The worm creates a program icon similar to the folder icon used by Windows Explorer. When the icon is executed, it opens the "My Documents" folder with Windows Explorer.


Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • Enforce a password policy. Complex passwords make it difficult to crack password files on compromised computers. This helps to prevent or limit damage when a computer is compromised.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a threat exploits one or more network services, disable, or block access to, those services until a patch is applied.
  • Always keep your patch levels up-to-date, especially on computers that host public services and are accessible through the firewall, such as HTTP, FTP, mail, and DNS services.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. Perform a forensic analysis and restore the computers using trusted media.
  • Train employees not to open attachments unless they are expecting them. Also, do not execute software that is downloaded from the Internet unless it has been scanned for viruses. Simply visiting a compromised Web site can cause infection if certain browser vulnerabilities are not patched.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

Writeup By: Paul Mangan

Discovered: August 17, 2006
Updated: February 01, 2007 5:06:08 PM
Also Known As: W32/Narcha-C [Sophos]
Type: Worm
Infection Length: Varies (24 kilobytes to 27 kilobytes + random appended data of up to 15 kilobytes)
Systems Affected: Windows

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Disable System Restore (Windows Me/XP).
  2. Update the virus definitions.
  3. Run a full system scan.
  4. Delete any values added to the registry.

For specific details on each of these steps, read the following instructions.

1. To disable System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you 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, 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:

Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, reenable System Restore by following the instructions in the aforementioned documents.

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).

2. To update the virus definitions
Symantec Security Response fully tests all the virus definitions for quality assurance before they are posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Running LiveUpdate, which is the easiest way to obtain virus definitions.
  • Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted daily. You should download the definitions from the Symantec Security Response Web site and manually install them. To determine whether definitions for this threat are available by the Intelligent Updater, refer to Virus Definitions (Intelligent Updater).

The latest Intelligent Updater virus definitions can be obtained here: Intelligent Updater virus definitions . For detailed instructions read the document: How to update virus definition files using the Intelligent Updater .

3. To run a full system scan
  1. Start your Symantec antivirus program and make sure that it is configured to scan all the files.
  2. Run a full system scan.
  3. If any files are detected, follow the instructions displayed by your antivirus program.
Important: If you are unable to start your Symantec antivirus product or the product reports that it cannot delete a detected file, you may need to stop the risk from running in order to remove it. To do this, run the scan in Safe mode. For instructions, read the document, How to start the computer in Safe Mode . Once you have restarted in Safe mode, run the scan again.

After the files are deleted, restart the computer in Normal mode and proceed with the next section.

Warning messages may be displayed when the computer is restarted, since the threat may not be fully removed at this point. You can ignore these messages and click OK. These messages will not appear when the computer is restarted after the removal instructions have been fully completed. The messages displayed may be similar to the following:

Title: [FILE PATH]
Message body: Windows cannot find [FILE NAME]. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search.

4. To delete the value from the registry
Important: Symantec strongly recommends that you back up the registry before making any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify the specified subkeys only. For instructions refer to the document: How to make a backup of the Windows registry .
  1. Click Start > Run.
  2. Type regedit
  3. Click OK.

    Note: If the registry editor fails to open the threat may have modified the registry to prevent access to the registry editor. Security Response has developed a tool to resolve this problem. Download and run this tool, and then continue with the removal.

  4. Navigate to the registry subkey:


  5. In the right pane, delete the following value:

    "Microsoft Agent" = "%System%\SVCH0ST.exe"

  6. Exit the Registry Editor.

Writeup By: Paul Mangan