W32.Gruel@mm

SUMMARY

W32.Gruel@mm is a worm that spreads by email and file-sharing networks. Its payload includes changing user passwords, hiding drive C, and making numerous changes to the system registry.

The email has the following characteristics:
Subject: Microsoft Windows Critical Update.
Attachment: Windows Critical Update 088562.exe
or
Subject: Symantec: New serious virus found
Attachment: Symantec_Norton_Tool.exe
or
Subject: Microsoft Windows Critical Update
Attachment: AntiVirus_Patch.exe

Behavior

Symptoms

Transmission

Protection

• Virus Definitions (LiveUpdate™ Weekly) July 16, 2003
• Virus Definitions (Intelligent Updater) July 14, 2003

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: High
• Large Scale E-mailing: Mass mailing to all the names in the Outlook Address book.
• Deletes Files: Deletes system files.
• Degrades Performance: Opens multiple Control Panel windows, which can cause the system to crash. "Hides" drive C from Windows. Changes access to executable files.
• Compromises Security Settings: Has a random routine that forces the user to change passwords.

Distribution

• Distribution Level: High
• Subject of Email: Microsoft Windows Critical Update OR Symantec: New serious virus found
• Name of Attachment: Windows Critical Update 088562.exe OR Symantec_Norton_Tool.exe OR AntiVirus_Patch.exe
• Size of Attachment: 104,200 bytes
• Shared Drives: Attempts to spread through file-sharing networks.

TECHNICAL DETAILS

When W32.Gruel@mm is run, it performs the following actions:

1. Deletes, or attempts to delete, the following files:
   • C:Autoexec.bat
   • C:Config.sys
   • C:WINNTSystem32*.dll
   • C:WINNTSystem32Ntoskrnl.exe
   • C:WINNTSystem32Command.com
   • C:WINNTRegedit.exe
   • C:WindowsSystem32Ntoskrnl.exe
   • C:WindowsSystem32Command.com
   • C:WindowsRegedit.exe
   • C:WINNTSystem32*.exe
   • C:WINNTSystem32*.com
   • C:WINNTSystem32*.ocx
   • C:WindowsSystem32*.dll
   • C:WindowsSystem32*.ocx
   • C:WindowsSystem32*.exe
   • C:WindowsSystem32*.com
     
     
2. Copies itself as the Hidden system file, C:Rundll32.exe.
   
   
3. Copies itself to C:windowsProgram FilesKazaaMy Shared FolderWindows XP KeyGen 2.5.exe.
   
   
4. Changes the Value data of the (Default) value to:
   
   <filename of worm> %1
   
   the following registry keys and values:
   
   HKEY_CLASSES_ROOTexefileshellopencommand
   
   HKEY_CLASSES_ROOTcomfileshellopencommand
   
   HKEY_CLASSES_ROOTatfileshellopencommand
   
   HKEY_CLASSES_ROOTpiffileshellopencommand
   
   HKEY_CLASSES_ROOThtafileshellopencommand
   
   HKEY_CLASSES_ROOThtfileshellopencommand
   
   As a result of these changes, the worm runs every time one of the aforementioned program types is executed.
   
   
5. Sets the following registry keys and values:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   "MediaPath"="C:Proyecto1.exe"
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRunOnce
   "Rundll32.exe"="C:Rundll32.exe"
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRunOnceEX
   "DevicePath" ="C:Proyecto1.exe"
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionSETUP
   "NetCache"="C:Proyecto1.exe"
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   "ProxyDevice"="C:Proyecto1.exe"
   
   HKEY_CURRENT_USERSoftwarekIlLeRgUaTe 1.03
   
   
6. Displays a false message that Windows has found an error and asks you to submit the error to Microsoft. There are two buttons displayed in this "warning" message, "Send Error" and "Send and Close."
   • If you click "Send Error," a fake error log is displayed.
   • If you try to cancel the message, the message is repeatedly displayed. Clicking "Back" returns you to the original "warning" message.
   • If you click "Send and Close" the following actions occur:
     • Multiple Control Panel windows open.
     • The CD-ROM drive opens
     • A message from the author of this threat is displayed, and this message cannot be moved or closed.
     • The System Tray is disabled.
     • The Task Bar disappears.
     • Drive C is no longer visible and all the icons disappear.
     • Only open windows remain. The message windows, which the worm generates, obscure them.
       
       
7. Attempts to mail itself to all the addresses in the Microsoft Outlook Address book.
   The email is formatted as follows:
   
   Subject: Microsoft Windows Critical Update.
   
   Message body:
   Critical Update: The Microsoft Windows updates found on this patch include fixes to following Windows operating systems: Any update that is critical to the operation of your computer is considered a Critical Update, and is automatically selected for installation during the scan for available updates. This patch is provided to help resolve known issues, and to protect your computer from known security vulnerabilities and all kinds of viruses. Whether a patch applies to your operating system, software programs, or hardware, it is listed in the Critical Updates category, like this patch attached. For Support please contact us at support@microsoft.com.
   
   Attachment: Windows Critical Update 088562.exe
   or
   Attachment: AntiVirus_Patch.exe
   
   or
   
   Subject: Symantec: New serious virus found
   
   Message body:
   Norton Security Response: has detected a new virus in the Internet. For this reason we made this tool attachement, to protect your computer from this serious virus. Due to the number of submissions received from customers, Symantec Security Response has upgraded this threat to a Category 5 (Maximum )
   
   Attachment: Symantec_Norton_Tool.exe

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

What you need to do depends on whether W32.Gruel@mm has actually executed.

If W32.Gruel@mm has already executed
If W32.Gruel@mm has run, it is possible that you will no longer be able to start Windows. (The damage the worm does will vary with both the operating system and the installation path.) Even if you can start Windows, once W32.Gruel@mm runs, it makes numerous changes to the registry and attempts to delete the system files.

In this situation, you must replace the deleted files and the Windows registry either from a clean backup, or by re-installing the operating system.

Once you have replaced the registry with a clean copy and restored any missing system files, update the virus definitions and run a full system scan as described in the next section.


If W32.Gruel@mm has not yet executed
If your Symantec antivirus product detects W32.Gruel@mm, delete it. If you suspect that the W32.Gruel@mm file exists on your hard drive, but has not yet executed, follow these steps:

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

1. Disable System Restore (Windows Me/XP).
2. Update the virus definitions.
3. Run a full system scan and delete all the files detected as W32.Gruel@mm.

For specific details on each of these steps, read the following instructions.

1. Disabling System Restore (Windows Me/XP)
If you are running Windows Me or Windows XP, we recommend that you temporarily turn off System Restore. Windows Me/XP uses this feature, which is enabled by default, to restore the files on your computer in case they become damaged. If a virus, worm, or Trojan infects a computer, System Restore may back up the virus, worm, or Trojan on the computer.

Windows prevents outside programs, including antivirus programs, from modifying System Restore. Therefore, antivirus programs or tools cannot remove threats in the System Restore folder. As a result, System Restore has the potential of restoring an infected file on your computer, even after you have cleaned the infected files from all the other locations.

Also, a virus scan may detect a threat in the System Restore folder even though you have removed the threat.

For instructions on how to turn off System Restore, read your Windows documentation, or one of the following articles:

• "How to disable or enable Windows Me System Restore"
• "How to turn off or turn on Windows XP System Restore"

For additional information, and an alternative to disabling Windows Me System Restore, see the Microsoft Knowledge Base article, "Antivirus Tools Cannot Clean Infected Files in the _Restore Folder," Article ID: Q263455.

2. 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.

3. 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.Gruel@mm, click Delete.