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Discovered: November 22, 2004
Updated: February 13, 2007 12:30:14 PM
Also Known As: Email-Worm.Win32.Yanz.b [Kaspe, W32/Yanz.b@MM [McAfee], W32/Yanz.B.worm [Panda], W32/Favsin-A [Sophos]
Type: Worm
Systems Affected: Windows

W32.Yanz.B@mm is a mass-mailing worm that uses its own SMTP engine to send itself to the email addresses that it retrieves from the infected computer.

This threat is written in the Microsoft Visual C++ programming language.

Antivirus Protection Dates

  • Initial Rapid Release version November 23, 2004
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version November 23, 2004
  • Latest Daily Certified version August 09, 2016 revision 001
  • Initial Weekly Certified release date November 23, 2004

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

Writeup By: Yana Liu

Discovered: November 22, 2004
Updated: February 13, 2007 12:30:14 PM
Also Known As: Email-Worm.Win32.Yanz.b [Kaspe, W32/Yanz.b@MM [McAfee], W32/Yanz.B.worm [Panda], W32/Favsin-A [Sophos]
Type: Worm
Systems Affected: Windows

When W32.Yanz.B@mm is executed, it performs the following actions:

  1. Displays a message box with the following text:

    • Title: WINDOWS PANIC
    • Message: No Windows. Yes doors and holes.

  2. Copies itself as the following:

    • %System%\Dong_Shi.exe
    • %System%\NvCpl.EXE

      Note: %System% is a variable that refers to the System folder. By default this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  3. Creates the following files:

    • C:\Yanzi.htm
    • %Windir%\Sun_YanZI.zip (a zip file that contains a file Sun_Yan_Zi-Shen_Q1.mp3.pif - it is a copy of the worm)
    • %System%\Huai_Tian_Q1.sys ( an MIME-encoded zip file that contains a file Sun_Yan_Zi-Shen_Q1.mp3.pif - it is a copy of the worm)
    • %System%\I_am_Sun_Yanzi.sys. (an MIME-encoded worm)
    • YanZi.vbs. (this file is created in the current folder and it creates the file sun.exe)

      Note: %Windir% is a variable that refers to the Windows installation folder. By default, this is C:\Windows or C:\Winnt.

  4. When the file sun.exe runs, it creates three .jpg files under %Temp% folder. The file names have "SuN" as prefix.

    • One of these files is a Trojan that exploits the Microsoft GDI+ Library JPEG Segment Length Integer Underflow vulnerability (described in the Microsoft Security Bulletin MS04-028) to download and execute a file named m00.exe, from the domain sunyanzi.fastmail.cn. This file is also a Trojan.
    • %Temp% is a variable that refers to the Windows temporary folder. By default, this is C:\Windows\TEMP (Windows 95/98/Me/XP) or C:\WINNT\Temp (Windows NT/2000).

  5. Adds the value:


    to the registry key:


    so that the worm runs every time Windows starts.

  6. Creates a mutex "Stefanie Sun Yanzi", which allows only one instance of the worm to run.

  7. Copies itself to folders on the infected machine that contain the string "SHAR" as follows:
    • SunYanZi.mp3.exe
    • Sun_YanZi-Huai_Tian_Qi.mpg.exe
    • Sun_YanZi-I_am_not_sad.mp3.exe
    • Sun_YanZi-Leave_me_alone.mp3.exe
    • Sun_YanZi-Mei_You_Ren_De_Fang_Xiang.avi.exe
    • Sun_YanZi-Shen_Qi.exe
    • Sun_YanZi-Tao_Wang.mpeg.exe
    • YanZi.Mp3.exe
    • YanZi_SuN-forever.mp3.exe

  8. Retrieves email addresses from the Windows address book and from the files with the following extensions:
    • .adb
    • .asp
    • .dbx
    • .doc
    • .htm
    • .html
    • .jsp
    • .rtf
    • .txt
    • .xml

  9. Avoids to send itself to the email addresses that contain the following substrings:
    • @aksam
    • @dostmail
    • @e-kolay
    • @erdemir
    • @erdemironline
    • @hurriyetim
    • @milliyet
    • @mynet
    • @ntvmsnbc
    • @posta
    • @sabah
    • @superonline

  10. Uses its own SMTP engine to send itself to all the email addresses that it finds. The email has the following characteristics:

    From: (Spoofed - One of the following strings, followed by @[recipient domain])
    • Asia_Singer
    • Great_Asia_Singer
    • Stefanie Sun Yanzi
    • Sun_YanZi
    • Sun_YanZi_Hayrani
    • Sun_Yan_Zi

      Subject: (One of the following)
    • Forever Sun Yanzi
    • Great_Asia_Singer
    • Hoscakal
    • I_hate_Spyware
    • SuN_YanZi_innocent
    • Sun-YanZi-Mp3-Archive
    • Sun_YanZi_Hayrani

      Message: (One of the following):
    • I can not contact you. Because, I am far to you(Turkiye)
    • I want to meet Sun YanZi. I am loving Sun-YanZi's Magic. Call me YanZi. But you don't contact me(Turkiye).
    • I want to see Sun YanZi. Call me Sun Yan Zi ;)
    • My Favourite Singer is Stefanie Sun Yanzi
    • Please listen to me Stefanie Sun Yanzi.
    • You must to listen Sun Yanzi. I am enjoying to listen Sun YanZi.

      Attachments: (One of the following with a .zip, .scr, or .pif extension)
    • Sun_YanZi
    • Huai_Tian_Qi
    • Sun_Yanzi_Mp3
    • Great_Asia_Singer
    • World_Tour_Sun_YanZi


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: Yana Liu

Discovered: November 22, 2004
Updated: February 13, 2007 12:30:14 PM
Also Known As: Email-Worm.Win32.Yanz.b [Kaspe, W32/Yanz.b@MM [McAfee], W32/Yanz.B.worm [Panda], W32/Favsin-A [Sophos]
Type: Worm
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 and delete all the files detected asW32.Yanz.B@mm.
  4. 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 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 withW32.Yanz.B@mm, 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.)

4. 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 value:


  5. Exit the Registry Editor.

Writeup By: Yana Liu