W32.Miroot.Worm

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Discovered: January 03, 2004
Updated: February 13, 2007 12:15:43 PM
Also Known As: W32/Legemer.worm [McAfee]
Type: Worm
Systems Affected: Windows


W32.Miroot.Worm is a worm that attempts to spread through network shares and the QQ instant messaging program. This worm also attempts to steal passwords for the online game, Legend of Mir 2.

Antivirus Protection Dates

  • Initial Rapid Release version January 05, 2004
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version January 05, 2004
  • Latest Daily Certified version August 09, 2016 revision 001
  • Initial Weekly Certified release date January 07, 2004

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

Writeup By: Heather Shannon

Discovered: January 03, 2004
Updated: February 13, 2007 12:15:43 PM
Also Known As: W32/Legemer.worm [McAfee]
Type: Worm
Systems Affected: Windows


When W32.Miroot.Worm is executed, it performs the following actions:

  1. Copies itself as:
    • C:\Cmd.exe
    • %System%\Rundll32.exe

      with hidden, system, and read-only attributes.


      Note: %System% is a variable. The worm locates the System folder and copies itself to that location. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  2. Creates the file, rundll32.exe.tmp (Windows 2000 only).

  3. May cause Windows to display the following error message (Windows 2000 only):




  4. Queries the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\
    Network\LanMan

    to find shared network folders.

  5. Makes two copies of itself in each discovered shared folder. The file names consist of Chinese characters, represented in hexadecimal as:
    • \xB2\xA1\xB6\xBE\xD7\xA8\xC9\xB1.exe
    • \xD6\xDC\xBD\xDC\xC2\xD7\xD1\xDD\xB3\xAA\xBB\xE1.exe

  6. Sets the value:

    "LoadPowerProfile"="%System%\Rundll32.exe"

    in the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

    so that the worm runs when you start Windows.

  7. Sets the value:

    "(Default)"="C:\cmd.exe %1 %*"

    in the registry key:

    HKEY_CLASSES_ROOT\exefile\shell\open\command

    so that the worm is restarted every time an executable file is opened.

  8. Adds an HTML link to outgoing QQ instant messages. If a vulnerable browser opens the link, the worm will be automatically downloaded and executed.

  9. Saves Legend of Mir password information to the file, C:\Cqsys.sys.

  10. Connects to an SMTP server and send the stolen information via email.

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: Heather Shannon

Discovered: January 03, 2004
Updated: February 13, 2007 12:15:43 PM
Also Known As: W32/Legemer.worm [McAfee]
Type: Worm
Systems Affected: Windows


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

  1. Update the virus definitions.
  2. Restart the computer in Safe mode or VGA mode.
  3. Make a copy of regedit.exe as regedit.com. Use regedit.com to reverse the changes made to the registry.
  4. Run a full system scan and delete all the files detected as W32.Miroot.Worm.
For details on each of these steps, read the following instructions.

1. Updating 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.


2. Restarting 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.

3. Copying Regedit.exe to Regedit.com, and reversing the changes made to 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.

Because the worm modified the registry so that it starts when you run the .exe files, first make a copy of the Registry Editor as a file with the .com extension:
  1. Do one of the following, depending on the version of Windows you are running:
    • Windows 95/98 users:
      1. Click Start.
      2. Point to Programs.
      3. Click the MS-DOS Prompt. (A DOS window opens at the C:\Windows prompt.) Proceed to step B of this section.

    • Windows Me users:
      1. Click Start.
      2. Point to Programs.
      3. Point to Accessories.
      4. Click the MS-DOS Prompt. (A DOS window opens at the C:\Windows prompt.) Proceed to step B of this section.

    • Windows NT/2000 users:
      1. Click Start, and then click Run.
      2. Type command, and then press Enter. (A DOS window opens.)
      3. Type cd \winnt, and then press Enter.
      4. Go to step 2 of this section.

    • Windows XP users:
      1. Click Start, and then click Run.
      2. Type command, and then press Enter. (A DOS window opens.)
      3. Type the following:

        cd\
        cd \windows

        Press Enter after typing each one.

      4. Proceed to step B of this section.

  2. Type copy regedit.exe regedit.com

    and then press Enter.

  3. Type regedit.com

    and then press Enter. (The Registry Editor opens in front of the DOS window.)

    After you finish editing the registry, exit the Registry Editor, and then exit the DOS window as well.

  4. Before continuing, 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. For instructions, read the document, "How to make a backup of the Windows registry."

  5. Navigate to and select the key:

    HKEY_LOCAL_MACHINE\Software\Classes\exefile\shell\open\command


    NOTE: The HKEY_LOCAL_MACHINE\Software\Classes key contains many subkey entries that refer to other file extensions. One of these file extensions is .exe. Changing this extension can prevent any files ending with a .exe extension from running. Make sure that you completely browse through this path until you reach the \command subkey.

    Modify the HKEY_LOCAL_MACHINE\Software\Classes\exefile\shell\open\command subkey, shown in the following figure:

    <<=== NOTE: Modify this key.

  6. In the right pane, double-click the (Default) value.
  7. Delete the current value data, and then type:

    "%1" %*

    That is, type the characters: quote-percent-one-quote-space-percent-asterisk.

    NOTES
    • Under Windows 95/98/Me/NT, the Registry Editor automatically encloses the value within quotation marks. When you click OK, the (Default) value should look exactly like this:

      ""%1" %*"  

    • Under Windows 2000/XP, the additional quotation marks will not appear. When you click OK, the (Default) value should look exactly like this:

      "%1" %*

    • Make sure that you completely delete all the value data in the command key before typing the correct data. If you leave a space at the beginning of the entry, any attempt to run the program files will result in the error message, "Windows cannot find .exe." If this occurs, restart the entire process from the beginning of this documentand make sure that you completely remove the current value data.

  8. Navigate to the key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

  9. In the right pane, double-click the LoadPowerProfile value. (The Edit String dialog box appears.)

    Enter the following in the Value data field, then click OK:

    Rundll32.exe powrprof.dll,LoadCurrentPwrScheme


    Note: The LoadPowerProfile value may not be present on all the operating systems.

  10. Exit the Registry Editor.


4. Scanning for and deleting 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.Miroot.Worm, click Delete.


Writeup By: Heather Shannon