VBS.Merlin.B@mm

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Discovered: July 12, 2001
Updated: February 13, 2007 11:52:39 AM
Also Known As: VBS.Eva@mm, VBS.Merlin.A@mm
Type: Worm


VBS.Merlin.B@mm is mass-mailing worm written in the Visual Basic Scripting (VBS) language. The worm spreads by emailing itself to all contacts in the Microsoft Outlook address book. It can also spread across network drives and by using an IRC client. Its main payload creates 2,500 randomly-named folders in the root of drive C and places a text file in each of these folders. It is able to infect Microsoft Word template files, overwrite .exe files, and delete Windows system files.

Antivirus Protection Dates

  • Initial Rapid Release version July 12, 2001
  • Latest Rapid Release version September 28, 2010 revision 054
  • Initial Daily Certified version July 12, 2001
  • Latest Daily Certified version September 28, 2010 revision 036

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

Writeup By: Kaoru Hayashi

Discovered: July 12, 2001
Updated: February 13, 2007 11:52:39 AM
Also Known As: VBS.Eva@mm, VBS.Merlin.A@mm
Type: Worm


When executed, this worm does the following:

  1. It copies itself into the \Windows folder using a randomly generated file name.
  2. It drops the file C:\Windows\SexSells.html. The file is detected as VBS.Loveletter.Variant.
  3. It changes registry keys so that the worm is run whenever you open files that have the following extensions:
    • .js
    • .doc
    • .gif
    • .jpg
    • .htt
    • .bmp
    • .avi
    • .mpg
    • .shs
    • .mp3
  4. It changes registry keys to decrease the security level of the computer.
  5. It searches for other computers on the local network, and if any are found, it copies itself to them.
  6. It infects the Microsoft Word global template, Normal.dot.

    NOTE: Norton AntiVirus detects the infected template as W97M.Melissa.family.
  7. It deletes any messages from the Microsoft Outlook inbox that have the subject "Re: Microsoft Security Bulletin."
  8. It sends itself as an HTML email to all contacts in your Microsoft Outlook address book. The infected email message has the following characteristics:

    Subject: Re: Microsoft Security Bulletin
    Message: You need ActiveX enabled if you want to see this e-mail. Please open this message again and click accept ActiveX. Microsoft

    NOTE: The message is detected as VBS.Loveletter.Variant.
  9. The worm then modifies the Script.ini file and attempts to spread using mIRC.
  10. It checks extensions of files on the infected computer and performs the following actions, depending on the extension:
    • If the extension is .vbs, .vbe, or .wsh, the worm overwrites the files.
    • If the extension is .htm or .html, the worm overwrites them with the dropped file SexSells.html.
    • If the extension is .jpg or .mp3, the worm deletes them.
    • If the extension is .exe, .xls, or .com, the worm overwrites the files and adds the .vbs extension to the file name.
  11. The worm creates 2,500 randomly named folders in the root of drive C. Each of these folders contains a text file.
  12. The Microsoft Office user agent "Merlin" appears and speaks "Everybody need somebody! That's why I love you!"
  13. It then deletes the Regedit.exe file.
  14. Three or more days after the infection occurs, the worm deletes the following files:
    • C:\Windows\User.dat
    • C:\Windows\User.bak
    • C:\Windows\System.dat
    • C:\Windows\System.bak
    • C:\Windows\Regedit.exe
  15. It modifies the Autoexec.bat file to delete the contents of drive C the next time that the computer starts.
  16. On the 2nd of every month it:
    • Attempts to delete the system registry.
    • Attempts to download another .exe file and execute it.The .exe file it downloads is saved as C:\Windows\System\Cih.exe.
  17. It modifies the following registry keys:
    • HKEY_CLASSES_ROOT\.JS\
    • HKEY_CLASSES_ROOT\.DOC\
    • HKEY_CLASSES_ROOT\.GIF\
    • HKEY_CLASSES_ROOT\.JPG\
    • HKEY_CLASSES_ROOT\.HTT\
    • HKEY_CLASSES_ROOT\.BMP\
    • HKEY_CLASSES_ROOT\.AVI\
    • HKEY_CLASSES_ROOT\.MPG\
    • HKEY_CLASSES_ROOT\.SHS\
    • HKEY_CLASSES_ROOT\.MP3\
    • HKEY_CLASSES_ROOT\VBSFile\Editflags
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows Script Host\Settings\Remote
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows Script Host\Settings\Timeout
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows Script Host\Settings\Enabled
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows Script Host\Settings\TrustPolicy
    • 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\1004
    • 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\1004
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersion\Policies\Explorer\NoDesktop
    • HKEY_LOCAL_MACHINE\Software\
      Microsoft\Windows\CurrentVersion\Run


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: Kaoru Hayashi

Discovered: July 12, 2001
Updated: February 13, 2007 11:52:39 AM
Also Known As: VBS.Eva@mm, VBS.Merlin.A@mm
Type: Worm


Run LiveUpdate to make sure that you have the most recent virus definitions.

  1. Start Norton AntiVirus (NAV), and run a full system scan, making sure that NAV is set to scan all files.
  2. Delete any files detected as VBS.Merlin.B@mm.
  3. If the worm has run, then you must restore damaged or deleted files from a clean backup or reinstall the missing or damaged software. In some cases, you must reinstall Windows. The numerous changes to the registry can be changed manually from a recent backup, or by reinstalling Windows and any affected programs. Instructions on how to manually restore the registry are in the following section.

How to manually restore the changes that were made to the registry

CAUTION : We strongly recommend that you back up the system registry before making any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Please make sure you modify only the keys specified. Please see the document How to back up the Windows registry before proceeding.
  1. Click Start, and click Run. The Run dialog box appears.
  2. Type regedit and then click OK. The Registry Editor opens.r
  3. Navigate to and double-click the key

    HKEY_LOCAL_MACHINE\Software\CLASSES\
  4. Directly under this key, one at a time, look for each of the following subkeys:
    .js
    .doc
    .gif
    .jpg
    .htt
    .bmp
    .avi
    .mpg
    .shs
    .mp3
  5. For each one that exists, double-click the following value in the right pane:

    (default)

    The Edit String dialog box opens.
  6. Look at the text in the Value Data box. If the value has been changed "Eva", replace it with the correct text as shown in the following list:

    NOTE: These are the default values. If you installed software that changed these values, either change the value to the value assigned by that software, or reinstall the software.

    Subkey Name Change the value to:
    .js JSFile
    .doc WordPad.Document.1
    .gif giffile
    .jpg jpegfile
    .htt c
    .bmp Paint.Picture
    .avi AVIFile
    .mpg mpegfile
    .shs ShellScrap
    .mp3 mp3file
  7. Navigate to the key

    HKEY_LOCAL_MACHINE\Software\CLASSES\VBSFile
  8. In the right pane, delete the value

    Editflags
  9. Navigate to the following key and delete it:

    HKEY_LOCAL_MACHINE\Software\CLASSES\Eva
  10. Navigate to the key

    HKEY_LOCAL_MACHINE\Software\Microsoft\
    Windows\CurrentVersion\Run
  11. In the right pane, look for values that have a random-letter name, for example:

    AOIFLKDBNFOIFSDSFKLSDF

    The Value Data of this will look similar to

    wscript.exe C:\WINDOWS\AOIFLKDBNFOIFSDSFKLSDF.doc.vbs %

    Delete any such values that you find.
  12. Navigate to the key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\
    Windows\CurrentVersion\
  13. In the right pane, double-click

    Registered Owner
  14. In the Value Data box, replace VBS.Eva@mm" with the name of the registered owner of the installed copy of Windows.
  15. Navigate to the keys

    HKEY_CURRENT_USER\Software\Microsoft\
    Office\9.0\Word\Security
  16. In the right pane, double-click the value:

    Level
  17. In the ValueData box, replace the value 1 with the value 3, and then click OK.
  18. Navigate to each of the keys in the following list. For each one, in the right pane, double-click the value. In the ValueData box, replace the value 1 with the value 0, and then click OK.

    NOTE: In the following list, the value that you must double-click appears at the end of each key. For example, for the first key in the list, select the key

    HKEY_CURRENT_USER\Software\Microsoft\
    Windows\CurrentVersions\Internet Settings\Zones\0

    in the left pane, and double-click the value

    1200

    in the right pane. Then replace the value 1 with the value 0.
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersions\Internet Settings\Zones\0\1200
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersions\Internet Settings\Zones\0\1201
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersions\Internet Settings\Zones\0\1004
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersions\Internet Settings\Zones\1\1200
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersions\Internet Settings\Zones\1\1201
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersions\Internet Settings\Zones\1\1004
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersions\Internet Settings\Zones\3\1200
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersions\Internet Settings\Zones\3\1201
    • HKEY_CURRENT_USER\Software\Microsoft\
      Windows\CurrentVersions\Internet Settings\Zones\3\1004
  19. Navigate to and delete the key

    HKEY_CURRENT_USER\Software\Microsoft\
    Windows Scripting Host\
  20. Navigate to the key

    HKEY_CURRENT_USER\Software\Microsoft\
    Windows\CurrentVersion\Policies\Explorer\
  21. In the right pane, select "NoDesktop" and delete it.
  22. Exit the Registry Editor.


Writeup By: Kaoru Hayashi