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  3. VBS.Redlof.A

VBS.Redlof.A

Risk Level 2: Low

Discovered:
April 16, 2002
Updated:
February 13, 2007 11:38:48 AM
Also Known As:
VBS/Redlof@M [McAfee], VBS.Redlof [AVP], VBS_REDLOF.A [Trend], VBS/Redlof-A [Sophos]
Type:
Virus
Systems Affected:
Windows 2000, Windows 95, Windows 98, Windows Me, Windows NT, Windows XP

When VBS.Redlof.A runs, it does the following:

It decrypts its viral body and then executes it.

Depending on the location of the Windows System folder, the virus copies itself as one of the following:
  • %Windir%\System\Kernel.dll
  • %Windir%\System\Kernel32.dll

NOTE: %Windir% is a variable. The worm locates the primary Windows installation folder (by default, this is C:\Windows or C:\Winnt) and copies itself to that location.

The virus makes the following changes to the registry to allow for the execution of the .dll files as script files:
  1. Verifies that the (Default) value of the registry key:

    HKEY_CLASSES_ROOT\.dll

    is equal to:

    dllfile

  2. For the registry key:

    HKEY_CLASSES_ROOT\.dll

    the virus verifies that the value:

    Content Type

    is equal to:

    application/x-msdownload


  3. In the registry key:

    HKEY_CLASSES_ROOT\dllFile

    the virus changes these subkeys:

    • DefaultIcon

      is changed to the same value as the value of the DefaultIcon subkey that is under the registry key:

      HKEY_CLASSES_ROOT\vxdfile

    • It adds the subkey ScriptEngine

      and changes its value to:

      VBScript

    • It adds the subkey ScriptHostEncode

      and changes its value to:

      {85131631-480C-11D2-B1F9-00C04F86C324}

  4. In the registry key:

    HKEY_CLASSES_ROOT\dllFile\Shell\Open\Command\

    the virus adds a (Default) value of:

    "%windir%\WScript.exe ""%1"" %*"

    or:

    "%windir%\System32\WScript.exe ""%1"" %*"

  5. In the registry key:

    HKEY_CLASSES_ROOT\dllFile\ShellEx\PropertySheetHandlers\WSHProps

    the virus sets the (Default) value to:

    {60254CA5-953B-11CF-8C96-00AA00B8708C}

  6. Copies itself as %Windir%\web\kwjall.gif.

The virus searches for the files that have the file extensions .html, .htm, .asp, .php, .jsp, .htt and .vbs in all the folders and on all the drives, and then infects those files.

VBS.Redlof.A spreads by adding itself as the default stationery that is used to create email messages. The virus:
  1. Either copies itself to C:\Program Files\Common Files\Microsoft Shared\Stationery\Blank.htm or, if that file already exists, it appends itself to the file.
  2. Sets Outlook Express to use stationery by default. To do this, in the registry key:

    HKEY_CURRENT_USER\Identities\[Default Use ID]\Software\Microsoft\
    Outlook Express\[Outlook Version].0\Mail

    the virus sets the value of :

    Compose Use Stationery

    to 1.

  3. Then, if the following values do not exist, they are created with the following value data:
    • In the registry key:

      HKEY_CURRENT_USER\Identities\[Default Use ID]\Software\Microsoft\
      Outlook Express\[Outlook Version].0\Mail


      the virus changes the value data of:

      Stationery Name

      to:

      C:\Program Files\Common Files\Microsoft Shared\Stationery\blank.htm

    • In the registry key:

      HKEY_CURRENT_USER\Identities\[Default Use ID]\Software\Microsoft\
      Outlook Express\[Outlook Version].0\Mail

      the virus changes the value data of:

      Wide Stationery Name

      to:

      C:\Program Files\Common Files\Microsoft Shared\Stationery\blank.htm

  4. In the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Office\9.0\Outlook\Options\Mail

    the virus sets the value data of:

    EditorPreference

    to:

    131072

  5. Next, if the following values do not exist, they are created and set to "blank":
    • The value:

      001e0360

      in the registry key:

      HKEY_CURRENT_USER\Software\Microsoft\Windows Messaging Subsystem\
      Profiles\Microsoft Outlook Internet Settings\0a0d020000000000c000000000000046

    • The value:

      001e0360

      in the registry key:

      HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\
      Windows Messaging Subsystem\Profiles\Microsoft Outlook Internet Settings\
      0a0d020000000000c000000000000046

    • The value:

      NewStationery

      in the registry key:

      HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Common\MailSettings


  6. In the registry key:

    HKEY_CURRENT_USER\Software\Microsoft\Office\
    10.0\Outlook\Options\Mail\EditorPreference


    the virus sets the value in:

    EditorPreference

    to:

    131072

  7. Finally, in the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

    the virus adds the value:

    Kernel32

    and sets it to:

    SYSTEM\Kernel32.dll
    or SYSTEM\Kernel.dll



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: Andre Post
Summary| Technical Details| Removal

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