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Symantec Security Response

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W32.Wallon.A@mm

Risk Level 2: Low

Discovered:
May 11, 2004
Updated:
February 13, 2007 12:22:57 PM
Also Known As:
WORM_WALLON.A [Trend], Win32.Wallon [Computer Associa, W32/Wallon.worm.a [McAfee], I-Worm.Wallon [Kaspersky]
Type:
Worm
Systems Affected:
Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows Server 2003, Windows XP

SUMMARY


W32.Wallon.A@mm is a mass-mailing worm that sends email messages containing a hyperlink to download the worm body from certain URLs. It also harvests the email addresses on the infected machine.

The worm exploits the following vulnerabilities: Microsoft Security Bulletin MS04-004 and Microsoft Security Bulletin MS04-013

This threat is written in Delphi and packed with ASPack.

Antivirus Protection Dates

  • Initial Rapid Release version May 12, 2004
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version May 12, 2004
  • Latest Daily Certified version September 28, 2010 revision 036
  • Initial Weekly Certified release date May 12, 2004
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Threat Assessment

Wild

  • Wild Level: Low
  • Number of Infections: 0 - 49
  • Number of Sites: 3 - 9
  • Geographical Distribution: Low
  • Threat Containment: Easy
  • Removal: Moderate

Damage

  • Damage Level: Low

Distribution

  • Distribution Level: Medium

TECHNICAL DETAILS


W32.Wallon.A@mm arrives as an email with a link in the message body. The email uses an Internet Explorer vulnerability, described in Microsoft Security Bulletin MS04-004, to display an obfuscated link. Clicking the link redirects the user to a Web site to download "wmplayer.exe" into the Windows Media Player folder. The Web site may attempt to exploit an Outlook Express vulnerability, described in Microsoft Security Bulletin MS04-013, to download and execute the file. Because the worm attempts to overwrite the Windows Media Player executable, any attempts to run Windows Media Player on an infected computer will execute a copy of the worm.

When wmplayer.exe is executed, it preforms the following actions:
  1. Creates the following registry keys:
    • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Extensions\
      {FE5A1910-F121-11d2-BE9E-01C04A7936B1}
    • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Extensions\
      {FE5A1910-F121-11d2-BE9E-01C04A7936B2}
    • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Extensions\
      {FE5A1910-F121-11d2-BE9E-01C04A7936B3}
    • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Extensions\
      {FE5A1910-F121-11d2-BE9E-01C04A7936B4}
    • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Extensions\
      {FE5A1910-F121-11d2-BE9E-01C04A7936B5}

      which creates five buttons on the Internet Explorer toolbar.

      Each button points to a URL starting with:

      http:/ /www.google.com.super-fast-search.apsua.com

      The last five buttons in the following screenshot are added by the worm:



  2. The worm also modifies the default home page of Internet Explorer to:

    http:/ /www.google.com.super-fast-search.apsua.com/fast-find.htm

    and the default search page to:

    http:/ /www.google.com.super-fast-search.apsua.com/search.htm

  3. Downloads a file from a predetermined URL and is saved as C:\Alpha.exe. The file is then executed, and remains memory-resident.

  4. Checks for the value:

    "Wh"="Yes"

    in the registry key:

    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer\Main

    creating it if not found, which serves as an infection marker.

  5. Collects email addresses from the Windows address book.

    The worm will ignore addresses containing the following strings:
    • microsoft
    • support
    • software
    • webmaster
    • postmaster
    • admin

  6. Uses its own SMTP engine to email itself to the addresses found.

    The email has the following characteristics:

    From:
    The worm uses information found in the following registry key to spoof the From: address of the email:

    HKEY_CURRENT_USER\Software\Microsoft\Internet Account Manager\Accounts

    Subject: RE:
    Message: Contains an obfuscated URI that appears to point to the Web site, http://drs.yahoo.com/<recipient's domain>/NEWS



  7. The worm may also send the list of email addresses found to the address 1@600pics.cjb.net.

  8. Periodically executes a remote cgi script located at http:/ /pixpox.com.


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.

REMOVAL


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. Restart the computer in Safe mode or VGA mode.
  4. Run a full system scan and delete all the files detected as W32.Wallon.A@mm.
  5. Delete the value that was added to the registry.
  6. Reset the Internet Explorer home page
  7. Reset the Internet Explorer Search page
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, 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 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).

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

3. To restart the computer in Safe mode or VGA mode

Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode or VGA mode.
  • For Windows 95, 98, Me, 2000, or XP users, restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."
  • For Windows NT 4 users, restart the computer in VGA mode.

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 W32.Wallon.A@mm, click Delete.
    Note: 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

WARNING: 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, 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_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer\Main
  4. In the right pane, delete the value:

    "Wh"="Yes"

  5. Navigate to the key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Extensions\
  6. Delete the subkeys:

    {FE5A1910-F121-11d2-BE9E-01C04A7936B1}
    {FE5A1910-F121-11d2-BE9E-01C04A7936B2}
    {FE5A1910-F121-11d2-BE9E-01C04A7936B3}
    {FE5A1910-F121-11d2-BE9E-01C04A7936B4}
    {FE5A1910-F121-11d2-BE9E-01C04A7936B5}
  7. Exit the Registry Editor.
6. To reset the Internet Explorer home page
  1. Start Microsoft Internet Explorer.
  2. Connect to the Internet, and then go to the page that you want to set as your home page.
  3. Click the Tools menu > Internet Options.
  4. In the Home page section of the General tab, click Use Current, and then click OK.

For additional information, or if this procedure does not work, read the Microsoft® Knowledge Base article, "Home Page Setting Changes Unexpectedly, or You Cannot Change Your Home Page Setting, Article ID 320159."

    7. To reset the Internet Explorer Search page
    Follow the instructions for your version of Windows

    Windows 98/Me/2000
    1. Start Microsoft Internet Explorer.
    2. Click the Search button on the toolbar.
    3. In the Search pane, click Customize.
    4. Click Reset.
    5. Click Autosearch Settings.
    6. Select a search site from the drop-down list, and then click OK.
    7. Click OK.

    Windows XP
    Because Windows XP is set by default to use animated characters in the search, how you do this can vary. Please read all instructions before you start.
    1. Start Microsoft Internet Explorer.
    2. Click the Search button on the toolbar.
    3. Do one of the following:
      • If the pane that opens looks similar to this picture:





        click the word Customize. Then skip to step h.

      • If the pane that opens has the words "Search Companion" at the top, and the center looks similar to this picture:





        click the "Change preferences" link as shown above. Proceed with step d.

    4. Click the "Change Internet search behavior" link.
    5. Under "Internet Search Behavior," click "With Classic Internet Search."
    6. Click OK. Then close Internet Explorer. (Close the program for the change to take effect.)
    7. Start Internet Explorer. When the search pane opens, it should now look similar to this:





      Click the word Customize, and then proceed with the next step.

    8. In the Search pane, click Customize.
    9. Click Reset.
    10. Click Autosearch Settings.
    11. Select a search site from the drop-down list, and then click OK.
    12. Click OK.
    13. Do one of the following:
      • If you were using (or want to continue using) the "Classic Internet Search" panel, stop here (or proceed with the next section).
      • If you want to go back to the "Search Companion" search (it usually has an animated character at the button), proceed with step n.

    14. Click the word Customize again.
    15. In the "Customize Search Settings" window, click "Use Search Companion," and then click OK.
    16. Close Internet Explorer. The next time you open it, it will again use the Search Companion.


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