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Discovered: September 13, 2001
Updated: February 13, 2007 11:57:54 AM
Also Known As: W32.Fanta.worm
Type: Trojan Horse
Systems Affected: Windows

Fanta.Trojan is a Trojan horse that steals the user name, passwords, and OICQ number; it sends the stolen information to the hacker's email address.

There are several versions of the threat. All of them are written in the Microsoft C++ programming language. Some version may be compressed with UPX.


  • Fanta.Trojan.Dr is a hacktool that can be used to generate Fanta.Trojan.
  • Definitions dated prior to November 6, 2002, may detect this threat as W32.Fanta.worm and may detect Fanta.Trojan.Dr as W32.Fanta.B.Worm.

Antivirus Protection Dates

  • Initial Rapid Release version September 14, 2001
  • Latest Rapid Release version November 03, 2019 revision 020
  • Initial Daily Certified version September 14, 2001
  • Latest Daily Certified version November 04, 2019 revision 060
  • Initial Weekly Certified release date September 14, 2001

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

Technical Description

When Fanta.Trojan runs, it does the following:

It copies itself as:

  • C:\%windir%\Winns.exe
  • C:\%system%\Syss.exe

  • %windir% is a variable. The Trojan locates the Windows installation folder (by default this is C:\Windows or C:\Winnt) and copies itself to that location.
  • %system% is a variable. The Trojan locates the \Windows\System folder (by default this is C:\Windows\System, C:\Windows\System32, or C:\Winnt\System32) and copies itself to that location.

It adds the value

msgserv_ C:\%Windir%\winns.exe

to the registry key


so that the Trojan runs when you start Windows.

The Trojan also inserts the text

shell=Explorer.exe winns.exe

in the [boot] section of the C:\Windows\System.ini file.

The Trojan steals the victim's information, such as user name, password, Windows version, processor identifier, dial-up phone number, and OICQ password. Then the Trojan sends the stolen information to a predefined email address.


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.


NOTE: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

  1. Update the virus definitions.
  2. Run a full system scan, and delete all files that are detected as Fanta.Trojan.
  3. (Windows 95/98/Me only) Remove the line that the Trojan added to C:\Windows\System.ini.
  4. Delete the value that the Trojan added to the registry key


For details on how to do this, read the following instructions.

To update the virus definitions:
All virus definitions receive full quality assurance testing by Symantec Security Response before being posted to our servers. There are two ways to obtain the most recent virus definitions:
  • Run LiveUpdate, which is the easiest way to obtain virus definitions. These virus definitions are posted to the LiveUpdate servers once each week (usually Wednesdays) unless there is a major virus outbreak. To determine whether definitions for this threat are available by LiveUpdate, look at the Virus Definitions (LiveUpdate) line at the top of this write-up.
  • Download the definitions using the Intelligent Updater. Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). They must be downloaded from the Symantec Security Response Web site and installed manually. To determine whether definitions for this threat are available by the Intelligent Updater, look at the Virus Definitions (Intelligent Updater) line at the top of this write-up.

    Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

To scan for and delete the infected files:
  1. Start your Symantec antivirus program, and make sure that it is configured to scan all files.
  2. Run a full system scan.
  3. If any files are detected as infected with Fanta.Trojan, click Delete.

To remove the line that the Trojan added to C:\Windows\System.ini:
This is necessary only on Windows 95/98/Me.

NOTE: (For Windows Me users only) Due to the file-protection process in Windows Me, a backup copy of the file that you are about to edit exists in the C:\Windows\Recent folder. Symantec recommends that you delete this file before you continue with the steps in this section. To do this using Windows Explorer, go to C:\Windows\Recent, and in the right pane select the Win.ini file and delete it. It will be regenerated as a copy of the file that you are about to edit when you save your changes to that file.
  1. Click Start, and click Run.
  2. Type the following, and then click OK.

    edit c:\windows\system.ini

    The MS-DOS Editor opens.

    NOTE: If Windows is installed in a different location, make the appropriate path substitution.
  3. In the [boot] section of the file, look for an entry that is similar to the following:

    shell=Explorer.exe winns.exe
  4. Delete the text


    so that the line reads only

  5. Click File, and click Save.
  6. Click File, and click Exit.

To remove the value that the Trojan added to the registry:

CAUTION : Symantec strongly recommends that you back up the registry before you make any changes to it. Incorrect changes to the registry can result in permanent data loss or corrupted files. Modify only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.
  1. Click Start, and click Run. The Run dialog box appears.
  2. Type regedit and then click OK. The Registry Editor opens.
  3. Navigate to the following key:

  4. In the right pane, delete the value

    msgserv_ C:\%Windir%\winns.exe
  5. Click Registry, and click Exit.

Writeup By: Yana Liu