Threat Explorer

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VBS.Merlin.A@mm

VBS.Merlin.A@mm

Discovered:
18 June 2001
Updated:
13 February 2007
Also Known As:
Bloodhound.VBS.worm

This worm sends itself to all entries in your Microsoft Outlook Address Book. It also sets itself to run at startup. Its main payload creates 500 randomly named folders in the root of drive C. It places a text file in each of these folders. It also has date-triggered payloads.

Antivirus Protection Dates

  • Initial Rapid Release version 18 June 2001
  • Latest Rapid Release version 28 September 2010 revision 054
  • Initial Daily Certified version 18 June 2001
  • Latest Daily Certified version 28 September 2010 revision 036
  • Initial Weekly Certified release date pending
Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

When executed, this worm does the following:
  1. It copies itself into the \Windows folder using a randomly generated file name.
  2. It drop the file C:\Windows\WindowsXP.html.
  3. It sends itself to all entries in your Microsoft Outlook Address Book. The infected email message has the following characteristics:

    Subject: WindowsXP Betatest
    Message:
    This message has permanent errors.
    Sorry
  4. Next, the worm creates 500 randomly named folders in the root of drive C. Each of these folders contains a text file.
  5. After creating the folders, the worm performs specific actions depending upon the day of the month:
    • On the 2nd of every month it:
      • Attempts to delete the system registry.
      • Deletes Regedit.exe.
      • Attempts to download another VBS worm and execute it.The file it downloads is saved as C:\WINDOWS\hp.exe. This file is set to run at startup using the registry. Once it is finished, it shuts down Windows.
    • On the 4th of every month it modifies the Autoexec.bat file to format drive C the next time that the computer starts. It then shuts down the computer.
    • On the 5th of every month it modifies the registry to change the Windows desktop.
    • On the 7th of every month it opens the Microsoft Agent and displays the message "Hör nicht auf zu strahlen, kleiner Stern!"
  6. It then modifies registry settings so that whenever files with the .mp3 or .avi extensions are executed, it will execute the viral code first.
  7. The worm then searches for files with the .vbs or .vbe extensions and appends itself to the original file.
  8. The worm attempts to spread the C:\Windows\WindowsXP.html file through mIRC by modifying the Script.ini file.
  9. It also modifies the following registry keys:
    • HKEY_CLASSES_ROOT\.mp3\
    • HKEY_CLASSES_ROOT\.avi\
    • HKEY_CLASSES_ROOT\VBSFile\Editflags
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows Script Host\Settings\Timeout
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows Script Host\Settings\Remote
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows Script Host\Settings\Enabled
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows Script Host\Settings\TrustPolicy
    • HKEY_CLASSES_ROOT\KleinerStern\shell\open\command\
    • HKEY_LOCAL_MACHINE\Software\Microsoft\
      Windows\CurrentVersion\RegisteredOwner
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersion\Internet Settings\Zones\0\1200
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersion\Internet Settings\Zones\0\1201
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersion\Internet Settings\Zones\0\1204
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersion\Internet Settings\Zones\1\1200
    • HKEY_CURRENT_USER\Software\Microsoft\Windows\
      CurrentVersion\Internet Settings\Zones\1\1201
    • HKEY_CURRENT_USER\Software\Microsoft\Windows\
      CurrentVersion\Internet Settings\Zones\1\1204
    • HKEY_CURRENT_USER\Software\Microsoft\Windows\
      CurrentVersion\Internet Settings\Zones\3\1200
    • HKEY_CURRENT_USER\Software\Microsoft\Windows\
      CurrentVersion\Internet Settings\Zones\3\1201
    • HKEY_CURRENT_USER\Software\Microsoft\Windows\
      CurrentVersion\Internet Settings\Zones\3\1204

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.

  1. Run LiveUpdate to make sure that you have the most recent virus definitions.
  2. Start Norton AntiVirus (NAV), and run a full system scan, making sure that NAV is set to scan all files.
  3. Delete any files detected as VBS.Merlin.A@mm.
  4. Restore the registry keys listed in the previous section to their original settings from a recent backup.


Writeup By: Douglas Knowles