W32.Miroot.Worm

SUMMARY

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.

Protection

• Virus Definitions (LiveUpdate™ Weekly) January 7, 2004
• Virus Definitions (Intelligent Updater) January 5, 2004

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 0 - 49
• Number of Sites: 0 - 2
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Difficult

Damage

• Damage Level: Low
• Payload Trigger: N/A
• Payload: N/A
• Large Scale E-mailing: N/A
• Deletes Files: N/A
• Modifies Files: N/A
• Releases Confidential Info: Steals game passwords.
• Degrades Performance: N/A
• Causes System Instability: N/A
• Compromises Security Settings: N/A

Distribution

• Distribution Level: Medium
• Subject of Email: N/A
• Name of Attachment: N/A
• Size of Attachment: N/A
• Ports: N/A
• Shared Drives: N/A
• Target of Infection: Shared drives, qq messages.
• Time Stamp of Attachment: N/A

TECHNICAL DETAILS

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.
     
     

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     Note: %System% is a variable. The worm locates the System folder and copies itself to that location. By default, this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).

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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_MACHINESoftwareMicrosoftWindowsCurrentVersion
   NetworkLanMan
   
   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:
   
   • xB2xA1xB6xBExD7xA8xC9xB1.exe
   • xD6xDCxBDxDCxC2xD7xD1xDDxB3xAAxBBxE1.exe
     
     
6. Sets the value:
   
   "LoadPowerProfile"="%System%Rundll32.exe"
   
   in the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   so that the worm runs when you start Windows.
   
   
7. Sets the value:
   
   "(Default)"="C:cmd.exe %1 %*"
   
   in the registry key:
   
   HKEY_CLASSES_ROOTexefileshellopencommand
   
   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":

• Turn off and remove unneeded services. By default, many operating systems install auxiliary services that are not critical, such as an FTP server, telnet, and a Web server. These services are avenues of attack. If they are removed, blended threats have less avenues of attack and you have fewer services to maintain through patch updates.
• If a blended 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 (for example, all Windows-based computers should have the current Service Pack installed.). Additionally, please apply any security updates that are mentioned in this writeup, in trusted Security Bulletins, or on vendor Web sites.
• 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.
• Configure your email server to block or remove email that contains file attachments that are commonly used to spread viruses, such as .vbs, .bat, .exe, .pif and .scr files.
• Isolate infected computers quickly to prevent further compromising your organization. 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.

REMOVAL

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

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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.

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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_MACHINESoftwareClassesexefileshellopencommand
   
   
   NOTE: The HKEY_LOCAL_MACHINESoftwareClasses 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_MACHINESoftwareClassesexefileshellopencommand 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_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   
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
   
   

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

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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.
   • For Norton AntiVirus consumer products: Read the document, "How to configure Norton AntiVirus to scan all files."
   • For Symantec AntiVirus Enterprise products: Read the document, "How to verify that a Symantec Corporate antivirus product is set to scan all files."
2. Run a full system scan.
3. If any files are detected as infected with W32.Miroot.Worm, click Delete.