W32.HLLW.Tang@mm

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Discovered: February 17, 2003
Updated: February 13, 2007 11:43:10 AM
Also Known As: W32/Gant@MM [McAfee], I-Worm.Tanger [KAV]
Type: Worm, Virus
Systems Affected: Windows


W32.HLLW.Tang@mm is a mass mailing worm that attempts to disguise itself as a file, which Windows does not recognize. The worm uses the icon of an unregistered file type to perform this.

W32.HLLW.Tang@mm emails itself to all the contacts in the Windows Address Book. It also attempts to spread itself through the file-sharing networks, IRC, Microsoft Word Documents, Microsoft Excel Spreadsheets and across mapped drives.

The worm is written in Microsoft Visual Basic (VB) and is compressed with UPX. The VB run-time libraries must be installed for the worm to be executed.

Antivirus Protection Dates

  • Initial Rapid Release version February 18, 2003
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version February 18, 2003
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date February 19, 2003

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

Writeup By: Robert X Wang

Discovered: February 17, 2003
Updated: February 13, 2007 11:43:10 AM
Also Known As: W32/Gant@MM [McAfee], I-Worm.Tanger [KAV]
Type: Worm, Virus
Systems Affected: Windows


When W32.HLLW.Tang@mm is executed, it does the following:

  1. Displays the following fake message, if the %System%\MSTng32.exe file does not exist on the computer:

    <filename> is not a valid Win32 application

    NOTE: <filename> is the full path and file name of the worm that was executed.
  2. Attempts to copy itself as some of the following files:
    • License.exe
    • %Windir%\EmailFix.exe
    • %Windir%\EmailGen.exe
    • %Windir%\EmailHacker.exe
    • %Windir%\Hilarious.scr
    • %Windir%\Keymapp32.exe
    • %Windir%\Mp3Connect.exe
    • %Windir%\Msdnssrv.exe
    • %Windir%\Msnetwrk32.exe
    • %Windir%\Msostart32.exe
    • %Windir%\Msregmc32.exe
    • %Windir%\Msscndsk.exe
    • %Windir%\Mwintype.exe
    • %Windir%\Notice.tng
    • %Windir%\PswdCrack.exe
    • %Windir%\Unicode32.scr
    • %Windir%\Windns32.exe
    • %Windir%\Wncnet32.exe
    • %Windir%\Wnetcon32.exe
    • %System%\Cmdinst32.exe
    • %System%\Dostng32.pif
    • %System%\Mscabdrv.exe
    • %System%\MSTng32.exe
    • %System%\Mswpdmgr.exe
    • %System%\Netwc32.exe
    • %System%\OMServ32.exe
    • %System%\Re-inst32.scr
    • %System%\Unitxt32.exe
    • %System%\Wincmndr.exe
    • %System%\Winlnkmgr.exe

      NOTES:
      • %Windir% is a variable. The worm 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 worm locates the System folder and copies itself to that location. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  3. Attempts to copy itself to all the mapped drives as License.exe.
  4. Scans the files in all the folders of all the local and mapped drives for files that have the .bat extension. The worm appends the following line to the end of each .bat file it finds:

    @if exist %system%\MSTng32.exe @win %systemMSTng32.exe
  5. Adds the value:

    Mstng32             %system%\MSTng32.exe

    to the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
  6. Creates the registry key:

    HKEY_USERS\.DEFAULT\Software\Zed/[rRlf]\Win32/TaNG

    and sets the default value of this key to:

    W32/TaNG by Zed/[rRlf]
  7. Searches all the local and mapped drives for the following folders:
    • Program Files\LimeWire\Shared
    • Programme\LimeWire\Shared
    • Programmi\LimeWire\Shared
    • Program Files\Gnucleus\Downloads
    • Programme\Gnucleus\Downloads
    • Programmi\Gnucleus\Downloads
    • Program Files\Gnucleus\Downloads\Incoming
    • Programme\Gnucleus\Downloads\Incoming
    • Programmi\Gnucleus\Downloads\Incoming
    • Program Files\Shareaza\Downloads
    • Programme\Shareaza\Downloads
    • Programmi\Shareaza\Downloads
    • Program Files\Kazaa\My Shared Folder
    • Programme\Kazaa\My Shared Folder
    • Programmi\Kazaa\My Shared Folder
    • Program Files\Kazaa Lite\My Shared Folder
    • Programme\Kazaa Lite\My Shared Folder
    • Programmi\Kazaa Lite\My Shared Folder
    • Program Files\BearShare\Shared
    • Programme\BearShare\Shared
    • Programmi\BearShare\Shared
    • Program Files\Edonkey2000\Incoming
    • Programme\Edonkey2000\Incoming
    • Programmi\Edonkey2000\Incoming
    • Program Files\Morpheus\My Shared Folder
    • Programme\Morpheus\My Shared Folder
    • Programmi\Morpheus\My Shared Folder
    • Program Files\Grokster\My Grokster
    • Programme\Grokster\My Grokster
    • Programmi\Grokster\My Grokster
    • Program Files\ICQ\Shared Files
    • Programme\ICQ\Shared Files
    • Programmi\ICQ\Shared Files
    • My Documents\My Music
    • My Music
    • Kazaa\My Shared Folder
    • My Downloads

  8. Searches all the files in each folder that it finds, described in step 7. If the worm finds any files whose extension is one of the following:
    • .scr
    • .pif
    • .mp3
    • .mp2
    • .gif
    • .bmp
    • .dib
    • .png
    • .jpg
    • .jpeg
    • .jpe
    • .tif
    • .tiff
    • .mpg
    • .mpeg
    • .mpe
    • .avi
    • .mov
    • .m3u
    • .b4s
    • .tmp
    • .txt
    • .lnk
    • .bat
    • .mdb
    • .ppt
    • .pps

      the worm attempts to delete the original file and copy itself as <original file name.ext>.exe.

      NOTE: <original file name.ext> is the full file name and extension of the file deleted by the worm. For example, if the worm finds the MyFile.scr file, the worm attempts to delete this file, and then copy itself as MyFile.scr.exe.

  9. Searches for these folders:
    • C:\Mirc
    • C:\Mirc32
    • C:\Program files\Mirc
    • C:\Programe\Mirc
    • C:\Programi\Mirc
    • C:\Program Files\Mirc32
    • C:\Programme\Mirc32
    • C:\Programmi\Mirc32

      and for each one W32.HLLW.Tang@mm finds, it overwrites the Script.ini file located in that folder, so that it can spread itself using mIRC.

  10. Searches for these folders:
    • C:\Pirch
    • C:\Pirch32
    • C:\Program Files\Pirch
    • C:\Programme\Pirch
    • C:\Programmi\Pirch
    • C:\Program Files\Pirch32
    • C:\Programme\Pirch32
    • C:\Programmi\Pirch32

      and for each one W32.HLLW.Tang@mm finds, it overwrites the Events.ini located in the folder, so that it can spread itself using Pirch.

  11. Searches for these folders:
    • C:\Virc
    • C:\Program Files\Virc
    • C:\Programme\Virc
    • C:\Programmi\Virc

      and, if any of the above folders is found, W32.HLLW.Tang@mm adds the value:

      Event17          dcc send $nick %windir%\Notice.pif

      to the registry key:

      HKEY_USERS\.DEFAULT\Software\MeGALiTH Software\
      Visual IRC96\Events

  12. Emails itself to all the contacts in the Windows Address Book.
  13. Creates the file, %Windir%\MSTngmgr32.ocx.

    NOTE: This file is the pure source code for the virus component's macro module. It is not in itself malicious, and as such, Symantec antivirus products do not detect it. Manually delete this file.
  14. Adds the values:

    AccessVBOM 1
    Level 1

    to the registry keys:

    HKEY_CURRENT_USER\Software\Microsoft\Office\<office version>\
    Word\Security
    HKEY_CURRENT_USER\Software\Microsoft\Office\<office version>\
    Excel\Security

    NOTE: <office version> varies with the version of Microsoft Office you have installed.
  15. Turns off the following options:
    • Microsoft Macro Virus Protection
    • Save Normal Prompt
    • Confirm Conversions
  16. Infects the Microsoft Word Normal.dot template.

    NOTE: The infected Word documents and templates will be detected as W97M.Tang.
  17. Overwrites the file, Personal.xls, in the Microsoft Excel Startup folder.

    NOTE: The infected Excel worksheets will be detected as X97M.Tang.


Email Routine Details

The worm uses Microsoft Outlook to email itself to all the contacts in the Windows Address Book. The email message is one of the following:

Subject : Important Notice
Attachment : EmailFix.exe
Message:
Hello readers,
A few days ago the Microsoft Network Email System automatically deleted my email account. This happened because there is a bug in the Microsoft Network
Email System that may unintentionally remove email accounts without prompting. I have included a patch with this email that will fix the bug on un-patched computers. If you need help installing this file, read attached help file.
Thanks.

Or:

Subject : Mp3 sites
Attachment : Mp3Connect.exe
Message:
Hello,

Try this new software that can download practically any .mp3 file that is found on the internet. I use this program all the time and I think it's great!

Have fun!

Or:

Subject : A ScreenSaver
Attachment : Hilarious.scr
Message:
Hello everyone,

I found a really funny ScreenSaver on the net yesterday and I think that you would find it funny like I did :) It's in the attachments.

Cya!

Or:

Subject : Email spoofer
Attachment : EmailGen.exe
Message:
Hello all,

Take a look at this email spoofer that I have included in the attachments. An email spoofer is a program that lets you email from anyone@anything.com!
it's really fun to use for pranks :)

Have fun!

Or:

Subject : Password Cracker
Attachment : PswdCrack.exe
Message :
Hello Everyone,

I have a cool Password Cracker for you in the attachments :) this Password Cracker can crack almost any password out there!
Try it for yorself!

Cya!

Or:

Subject : Hotmail passwords
Attachment : EmailHacker.exe
Message:
Hello Readers,

Have you tried to crack a Hotmail password ... and failed? Try the 'Hotmail Password Cracker' program that I have included in the attachments.

Happy hacking!

Recommendations

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: Robert X Wang

Discovered: February 17, 2003
Updated: February 13, 2007 11:43:10 AM
Also Known As: W32/Gant@MM [McAfee], I-Worm.Tanger [KAV]
Type: Worm, Virus
Systems Affected: Windows


These instructions pertain to 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.
    • Remove the text that the worm added to all the .bat files detected as W32.HLLW.Tang@mm.
    • Delete all the files, other than the .bat files, detected as W32.HLLW.Tang@mm.
  3. Reverse the changes that the worm made to the registry.
For specific details on each of these procedures, read the following instructions.

1. Updating 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 the 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), in the "Protection" section, at the top of this writeup.
  • Downloading the definitions using the Intelligent Updater. The Intelligent Updater virus definitions are posted on U.S. business days (Monday through Friday). 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), in the "Protection" section, at the top of this writeup.

    The 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.

2. Scanning for and fixing or deleting 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. If the files are detected as infected with W32.HLLW.Tang@mm, do the following:
    • If the infected file has the .bat extension, follow these steps:
      1. Write down the full path and file name of the .bat file.
      2. Continue the scan without deleting the file. When the scan is finished, for each detected .bat file, do the following:
        1. Click Start, and then click Run.
        2. Type the following:

          notepad <path\file name>

          and then click OK. (The file opens in Notepad.)

          For example, if the infected .bat file is C:\Special.bat, you would type:

          notepad c:\special.bat
      3. Look for a line similar to:

        @if exist %system%\MSTng32.exe @win %system%\MSTng32.exe
      4. If this line exists, be sure that you do not select any other text, and then delete this line.
      5. Click File, and then click Save.
      6. Click File, and then click Exit.
    • If the infected file does not have the .bat extension, click Delete.


4. Reversing the changes made 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 the specified keys only. Read the document, "How to make a backup of the Windows registry ," for instructions.
  1. Click Start, and then click Run. (The Run dialog box appears.)
  2. Type regedit

    Then click OK. (The Registry Editor opens.)
  3. Navigate to the key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  4. In the right pane, delete the value:

    Mstng32
  5. Delete the registry key:

    HKEY_USERS\.DEFAULT\Software\Zed/[rRlf]\W32/TaNG
  6. Navigate to the key:

    HKEY_USERS\.DEFAULT\Software\MeGALiTH Software\Visual IRC96\Events
  7. In the right pane, delete the value: Event17
  8. Navigate to the key:

    HKEY_CURRENT_USER\Software\Microsoft\Office\<office.version>\
    Word\Security
  9. In the right pane, delete the values:

    AccessVBOM
    Level
  10. Navigate to the key:

    HKEY_CURRENT_USER\Software\Microsoft\Office\<office.version>\
    Excel\Security
  11. In the right pane, delete the values:

    AccessVBOM
    Level
  12. Exit the Registry Editor.


Writeup By: Robert X Wang