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Discovered: October 19, 2004
Updated: February 13, 2007 12:28:51 PM
Also Known As: Backdoor.Win32.VB.un [Kaspersk, BackDoor-BDN [McAfee]
Type: Trojan Horse
Systems Affected: Windows

Trojan.Watsoon.A is a polymorphic Trojan horse that opens a backdoor on a compromised computer. By default is uses TCP port 19381

NOTE: . Definitions prior to 27th October 2004 may detect this threat as W32.Watsoon.A

Antivirus Protection Dates

  • Initial Rapid Release version October 20, 2004
  • Latest Rapid Release version October 08, 2017 revision 025
  • Initial Daily Certified version October 20, 2004
  • Latest Daily Certified version October 09, 2017 revision 002
  • Initial Weekly Certified release date October 20, 2004

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

Writeup By: John Canavan

Discovered: October 19, 2004
Updated: February 13, 2007 12:28:51 PM
Also Known As: Backdoor.Win32.VB.un [Kaspersk, BackDoor-BDN [McAfee]
Type: Trojan Horse
Systems Affected: Windows

When the Trojan is executed, it performs the following:

  1. Copies itself as one or more of the following file names:
    • %System%\drwatsoon.exe
    • %System%\krnl386Mem
    • %System%\mobsyncs.exe
    • %System%\ntsrvosi386.vxd

  2. Drops and executes a file named %System%\NClienti386.exe, which is detected as Backdoor.Trojan. This file provides the backdoor functionality of the Trojan, listening for remote connections on TCP port 1938.

  3. Once authenticated, the remote user will have full access to the system with the ability to perform any of the following actions.

    • Download and execute files
    • Upload/Download files
    • Execute files
    • Kill processes
    • Copy, move, or delete files and folders
    • Retrieve system information

  4. May drop and execute a file named %System%\Neti386, which is used to gather user account names and passwords.

  5. Adds the value:

    "Srv RPCrom"="%System%\NClienti386.exe"

    to the registry keys:


    so that Trojan.Watsoon.A runs every time Windows starts.

  6. Adds the values:

    "Sync Server"="%System%\drwatsoon.exe /n logon"
    "Srv RPCrom"="%System%\NClienti386.exe"

    to the registry key:


    so that Trojan.Watsoon.A runs every time Windows starts.

  7. Adds the following value:

    "Shell" = "explorer.exe drwatsoon.exe"

    to the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon

  8. Adds the following value:

    "load" = "%System%\mobsyncs.exe"

    to the registry key:

    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows

  9. Adds the following value:

    "AutoRun" = "echo off|%System%\mobsyncs.exe /n"

    to the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Command Processor

  10. May create one or more of the following services:

    • NTi386 Authorization Service
    • TCP/IP Mac Os
    • TCP/IP NetBios Service Manager
    • TCP/IP Routing Srv
    • Mac Client Service

  11. Drops a random number of copies of itself to the following locations:

    • %System%\[random filename]
    • %Start Menu%\[random filename]
    • %Start Menu%\Programs\[random filename]

      using some of the following file names:

    • ACD Wallpapers
    • Accounting Report
    • Adult on night
    • Adventure Stuff
    • Avril.L - Complicated
    • Backup on dec 2003
    • Bank data
    • Biblio
    • Black Book
    • Blue Laces 16
    • Blue Porn 17 age
    • Britney.s Feat Metalica - Sanitarium
    • Coffee Beans
    • Data Owner
    • Destiny Child - Say My Name
    • Don't Open Me
    • Eminem - Sex4Me
    • FBI Wanted
    • FeatherTextures
    • Fire Hole
    • Gone Fishings
    • Greenstones
    • Hacker Tutorial1
    • Hacker Tutorial2
    • Java - Bad Habbit
    • Java - The Virus
    • Last Archive
    • Limpbizkit - Eat you Alive
    • Limpbizkit - My Way
    • Limpbizkit Feat Korn - Destroy
    • My Hearts
    • Nirvana - Love Buzz
    • Nite Vision
    • Northwind
    • Oh ye Kiss Me now
    • Play And Destroy
    • Porn Articel
    • Porn baby
    • Prairie Winds
    • Rhododendrons
    • River Sumidas
    • SQL Replica
    • Sallary inc
    • Santa Fe Stuccos
    • Sepultura - Root
    • Setup its
    • Sex Penis
    • Sexy Honey
    • Soap Bubbless
    • Tonk Hawk - Intro Destroy
    • Try This if you have heart
    • Vagina
    • What up doc
    • Who is terrorist
    • Winnts
    • Zapotecs
    • dba Stored

      with one of the following extensions:

    • .exe
    • .pif
    • .scr

  12. Iterates through the hard drive of the infected host and may randomly drop copies of itself to the directories found with file names above.

  13. Monitors the process list and will attempt to kill the following processes:
    • regedit.exe
    • taskmgr.exe

  14. Attempts to log keystrokes, which are stored in a local log file. The remote user, who is connected via the backdoor, can pick up this log file.


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: John Canavan

Discovered: October 19, 2004
Updated: February 13, 2007 12:28:51 PM
Also Known As: Backdoor.Win32.VB.un [Kaspersk, BackDoor-BDN [McAfee]
Type: Trojan Horse
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. Find and stop the service.
  4. Run a full system scan and delete all the files detected as Trojan.Watsoon.A.
  5. Delete the value that was 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:

When you are completely finished with the removal procedure and are satisfied that the threat has been removed, re-enable 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: These virus definitions are posted to the LiveUpdate servers once each week (usually on Wednesdays), unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, refer to the Virus Definitions (LiveUpdate).
  • 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 the Virus Definitions (Intelligent Updater).

    The Intelligent Updater virus definitions are available: Read "How to update virus definition files using the Intelligent Updater" for detailed instructions.

3. To find and stop the service
  1. Click Start > Run.
  2. Type services.msc, and then click OK.
  3. Locate and select each of the services that are associated with Trojan.Watsoon.A.
  4. Click Action > Properties.
  5. Click Stop.
  6. Change Startup Type to Manual.
  7. Click OK and close the Services window.
  8. Restart the computer.
4. To scan for and delete the infected files
  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 as infected with Trojan.Watsoon.A, click Delete.

    If your Symantec antivirus product reports that it cannot delete an infected file, Windows may be using the file. To fix 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, you can leave the computer in Safe mode and proceed with section 4. When that is done, restart the computer in Normal mode.)

5. To delete the value from the registry

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 keys only. Read the document, "How to make a backup of the Windows registry ," for instructions.
  1. Click Start > Run.
  2. Type regedit

    Then click OK.

  3. Navigate to the key:


  4. In the right pane, delete the values:

    "Srv RPCrom"="%System%\NClienti386.exe"

  5. Navigate to the key:


  6. In the right pane, delete the values:

    "Sync Server" = "%System%\drwatsoon.exe /n logon"
    "Srv RPCrom"="%System%\NClienti386.exe"

  7. Navigate to the key:


  8. In the right pane, delete the values:

    "Sync Server" = "%System%\drwatsoon.exe /n logon"
    "Srv RPCrom"="%System%\NClienti386.exe"

  9. Navigate to the key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon

  10. In the right pane, delete the value:

    "Shell" = "explorer.exe drwatsoon.exe"

  11. Navigate to the key:

    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows

  12. In the right pane, delete the value:

    "load" = "%System%\mobsyncs.exe"

  13. Navigate to the key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Command Processor

  14. In the right pane, delete the value:

    "AutoRun" = "echo off|%System%\mobsyncs.exe /n"

  15. Exit the Registry Editor.

Writeup By: John Canavan