Threat Explorer

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VBS.Junkmail@mm

VBS.Junkmail@mm

Discovered:
10 December 2004
Updated:
13 February 2007
Systems Affected:
Windows

VBS.Junkmail@mm is a generic VBS mass-mailing worm, which copies itself to files on the C drive of the infected computer.

Antivirus Protection Dates

  • Initial Rapid Release version 10 December 2004
  • Latest Rapid Release version 07 October 2010 revision 007
  • Initial Daily Certified version 10 December 2004
  • Latest Daily Certified version 07 October 2010 revision 022
  • Initial Weekly Certified release date 15 December 2004
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

When VBS.Junkmail@mm runs, it performs the following actions:
  1. Searches for the files with the following extensions on the C drive of the infected computer:
    • .dll
    • .bmp
    • .jpg
    • .gif
    • .txt
    • .bat
    • .com
    • .mp3
    • .wma
    • .bkf

  2. Copies itself under the found file names and adds a .vbs extension. These copies include random junk comment lines inserted throughout the code, in an attempt to make the script appear polymorphic.

    Note: The worm may also attempt to delete the original files that it found. Depending on what files are deleted, this may cause the computer to be unable to reboot correctly.

  3. Attempts to copy itself as the following files:
    • %Windir%\SHELL32.vbs
    • %Windir%\MAPIDLL.vbs
    • %System%\NETDLL.vbs
    • XAUDIO_SOUND.MP3.VBE

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

  4. Attempts to send a mass-mailing by exploiting Microsoft Outlook and Outlook Express. The email has the following features:

    Subject: (One of the following)
    • Surprise
    • Important
    • Imformation

      Message body:
    • All you need to know... (in the audio file)

      Attachment:
    • XAUDIO_SOUND.MP3.VBE

  5. Sets the following value:

    "DisableTaskMgr" = "dword: 1"

    in the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System

    in an attempt to disable the Task Manager on NT systems.

  6. Sets the following value:

    "Timeout" = "dword: 0"

    in the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Windows Scripting Host\Setting

    in an attempt to disable the timeout of Win9X systems.

  7. Attempts to create the file %Windir%\readme.htm.

  8. Attempts to run a VB script that searches for all files with the following extensions:
    • .txt
    • .doc
    • .htm
    • .inf

  9. May add a random number of lines reading "I'm the BEST " to any file found.

    Note: The worm includes code that is intended to set the Run and RunServices keys in HKEY_LOCAL_MACHINE, but these keys are never written, making the worm non-extensible.


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.

The following instructions pertain to all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines.

What you need to do depends on whether VBS.Junkmail@mm has actually executed.

If VBS.Junkmail@mm has already executed
If VBS.Junkmail@mm has run, it is possible that you will no longer be able to start Windows. (The damage the worm does will vary with both the operating system and the installation path.) Even if you can start Windows, once VBS.Junkmail@mm runs, it makes numerous changes to the registry and attempts to delete the system files.

In this situation, you must replace the deleted files and the Windows registry either from a clean backup, or by reinstalling the operating system.

Once you have replaced the registry with a clean copy and restored any missing system files, update the virus definitions and run a full system scan as described in the next section.


If VBS.Junkmail@mm has not yet executed
If your Symantec antivirus product detects VBS.Junkmail@mm, delete it. If you suspect that the VBS.Junkmail@mm file exists on your hard drive, but has not yet executed, follow these steps:
  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 VBS.Junkmail@mm.
  5. Reverse the changes made to the registry.
For 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 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 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 VBS.Junkmail@mm, click Delete.


5. To reverse the changes made to the registry
Important: 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 registry subkey:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System

  4. In the right pane delete the value:

    "DisableTaskMgr" = "dword: 1"

  5. Navigate to registry subkey:

    HKEY_CURRENT_USER\Software\Microsoft\Windows Scripting Host\Setting

  6. In the right pane delete the value:

    "Timeout" = "dword: 0"

  7. Exit the Registry Editor.

  8. Restart the computer in Normal mode. For instructions, read the section on returning to Normal mode in the document, "How to start the computer in Safe Mode."


Writeup By: Maryl Magee