W32.Autex.C

SUMMARY

W32.Autex.C is a worm that spreads by copying itself to mapped drives on a compromised computer.

Protection

• Virus Definitions (LiveUpdate™ Weekly) September 28, 2005
• Virus Definitions (Intelligent Updater) September 24, 2005

Threat Assessment

Wild

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

Damage

• Damage Level: Low
• Payload: Copies itself to network shares.

Distribution

• Distribution Level: Medium

TECHNICAL DETAILS

Once executed, W32.Autex.C performs the following actions:

1. Copies itself as:
   
   
   • %Windir%1.com
   • %Windir%services.exe
   • %Windir%finder.com
   • %Windir%explorer.com
   • %Windir%exeroute.exe
   • %System%undll32.com
   • %System%finder.com
   • %System%command.pif
   • %System%msconfig.com
   • %System%dxdiag.com
   • %System%egedit.com
   • %ProgramFiles%Internet Exploreriexplore.com
   • %ProgramFiles%common filesiexplore.pif
     
     Note:
   • %System% is a variable that refers to the System folder. By default this is C:WindowsSystem (Windows 95/98/Me), C:WinntSystem32 (Windows NT/2000), or C:WindowsSystem32 (Windows XP).
   • %Windir% is a variable that refers to the Windows installation folder. By default, this is C:Windows (Windows 95/98/Me/XP) or C:Winnt (Windows NT/2000).
   • %ProgramFiles% is a variable that refers to the program files folder. By default, this is C:Program Files.
   • The files may have the Read-only, hidden, and system attributes set.
     
     
2. Adds the value:
   
   "Torjan Program" = "services.exe"
   
   to the registry subkeys:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersion
   RunServices
   
   so that it runs every time Windows starts.
   
   
3. Prepends finder.com to the values in the following registry subkeys:
   
   HKEY_CLASSES_ROOTscrfileshellinstallcommand
   HKEY_CLASSES_ROOTscriptletfileShellGenerate Typelibcommand
   HKEY_CLASSES_ROOT elnetshellopencommand
   HKEY_CLASSES_ROOTUnknownshellopenascommand
   HKEY_LOCAL_MACHINESOFTWAREClassesdunfileshellopencommand
   HKEY_LOCAL_MACHINESOFTWAREClassesInternetShortcutshell
   opencommand
   HKEY_LOCAL_MACHINESOFTWAREClassesscrfileshellinstallcommand
   HKEY_LOCAL_MACHINESOFTWAREClassesUnknownshellopenascommand
   HKEY_LOCAL_MACHINESOFTWAREClasses elnetshellopencommand
   
   
4. Prepends ExERoute.exe to the values in the following registry subkeys:
   
   HKEY_CLASSES_ROOTwinfilesShellOpenCommand
   HKEY_LOCAL_MACHINESOFTWAREClasseswinfilesShellOpenCommand
   
   
5. Prepends explorer.com to the values in the following registry subkeys:
   
   HKEY_CLASSES_ROOTDriveshellfindcommand
   HKEY_LOCAL_MACHINESOFTWAREClassesDriveshellfindcommand
   
   
6. Prepends rundll32.com to the values in the following registry subkeys:
   
   HKEY_CLASSES_ROOTcplfileshellcplopencommand
   HKEY_CLASSES_ROOTfileshellopencommand
   HKEY_CLASSES_ROOThtmlfileshellprintcommand
   HKEY_CLASSES_ROOTinffileshellInstallcommand
   HKEY_LOCAL_MACHINESOFTWAREClassescplfileshellcplopencommand
   HKEY_LOCAL_MACHINESOFTWAREClassesfileshellopencommand
   HKEY_LOCAL_MACHINESOFTWAREClasseshtmlfileshellprintcommand
   HKEY_LOCAL_MACHINESOFTWAREClassesinffileshellInstallcommand
   
   
7. Prepends iexplore.com to the values in the following registry subkeys:
   
   HKEY_CLASSES_ROOTApplicationsiexplore.exeshellopencommand
   HKEY_CLASSES_ROOTftpshellopencommand
   HKEY_LOCAL_MACHINESOFTWAREClassesApplicationsiexplore.exe
   shellopencommand
   HKEY_LOCAL_MACHINESOFTWAREClassesftpshellopencommand
   
   
8. Prepends iexplore.pif to the value of HKEY_CLASSES_ROOThttpshellopencommand
   
   
9. Creates the registry subkeys:
   
   HKEY_CLASSES_ROOTCLSID{871C5380-42A0-1069-A2EA-08002B30309D
   }shellOpenHomePageCommand
   HKEY_LOCAL_MACHINESOFTWAREClassesCLSID
   {871C5380-42A0-1069-A2EA-08002B30309D}shellOpenHomePageCommand
   
   
10. Modifies the value:
    
    "Check_Associations" = "yes"
    
    in the registry subkey:
    
    HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain
    
    
11. Scans mapped drive letters and creates a file named Autorun.inf in the root folder.

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. Disable System Restore (Windows Me/XP).
2. Update the virus definitions.
3. Run a full system scan and delete all the files detected.
4. Delete any values added to the registry.
   

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

1. To disable 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

Note: When you are completely finished with the removal procedure and are satisfied that the threat has been removed, reenable System Restore by following the instructions in the aforementioned documents.

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. To update 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 Virus Definitions (LiveUpdate).
• Downloading the definitions using the Intelligent Updater: The Intelligent Updater virus definitions are posted daily. 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 Virus Definitions (Intelligent Updater).
  
  The latest Intelligent Updater virus definitions can be obtained here: Intelligent Updater virus definitions. For detailed instructions read the document: How to update virus definition files using the Intelligent Updater.

3. To scan for and delete 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, click Delete.

Important: If you are unable to start your Symantec antivirus product or the product reports that it cannot delete a detected file, you may need to stop the risk from running in order to remove it. To do this, run the scan in Safe mode. For instructions, read the document, How to start the computer in Safe Mode. Once you have restarted in Safe mode, run the scan again.

After the files are deleted, restart the computer in Normal mode and proceed with the next section.

Warning messages may be displayed when the computer is restarted, since the threat may not be fully removed at this point. You can ignore these messages and click OK. These messages will not appear when the computer is restarted after the removal instructions have been fully completed. The messages displayed may be similar to the following:

Title: [FILE PATH]
Message body: Windows cannot find [FILE NAME]. Make sure you typed the name correctly, and then try again. To search for a file, click the Start button, and then click Search.


4. To delete the value from the registry
Important: 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 subkeys only. For instructions refer to the document: How to make a backup of the Windows registry.

1. Click Start > Run.
2. Type regedit
3. Click OK.
   
   Note: If the registry editor fails to open the threat may have modified the registry to prevent access to the registry editor. Security Response has developed a tool to resolve this problem. Download and run this tool, and then continue with the removal.
   
   
4. Navigate to the subkey:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersion
   RunServices
   
   
5. In the right pane, delete the value:
   
   "Torjan Program" = "services.exe"
   
   
6. Navigate to the subkeys:
   
   HKEY_CLASSES_ROOTscrfileshellinstallcommand
   HKEY_CLASSES_ROOTscriptletfileShellGenerate Typelibcommand
   HKEY_CLASSES_ROOT elnetshellopencommand
   HKEY_CLASSES_ROOTUnknownshellopenascommand
   HKEY_LOCAL_MACHINESOFTWAREClassesdunfileshellopencommand
   HKEY_LOCAL_MACHINESOFTWAREClassesInternetShortcutshell
   opencommand
   HKEY_LOCAL_MACHINESOFTWAREClassesscrfileshellinstallcommand
   HKEY_LOCAL_MACHINESOFTWAREClassesUnknownshellopenascommand
   HKEY_LOCAL_MACHINESOFTWAREClasses elnetshellopencommand
   
   
7. In the right pane, delete any reference to finder.com.
   
   
8. Navigate to the subkeys:
   
   HKEY_CLASSES_ROOTwinfilesShellOpenCommand
   HKEY_LOCAL_MACHINESOFTWAREClasseswinfilesShellOpenCommand
   
   
9. In the right pane, delete any reference to ExERoute.exe.
   
   
10. Navigate to the subkeys:
    
    HKEY_CLASSES_ROOTDriveshellfindcommand
    HKEY_LOCAL_MACHINESOFTWAREClassesDriveshellfindcommand
    
    
11. In the right pane, delete any reference to explorer.com.
    
    
12. Navigate to the subkeys:
    
    HKEY_CLASSES_ROOTcplfileshellcplopencommand
    HKEY_CLASSES_ROOTfileshellopencommand
    HKEY_CLASSES_ROOThtmlfileshellprintcommand
    HKEY_CLASSES_ROOTinffileshellInstallcommand
    HKEY_LOCAL_MACHINESOFTWAREClassescplfileshellcplopencommand
    HKEY_LOCAL_MACHINESOFTWAREClassesfileshellopencommand
    HKEY_LOCAL_MACHINESOFTWAREClasseshtmlfileshellprintcommand
    HKEY_LOCAL_MACHINESOFTWAREClassesinffileshellInstallcommand
    
    
13. In the right pane, delete any reference to rundll32.com.
    
    
14. Navigate to the subkeys:
    
    HKEY_CLASSES_ROOTApplicationsiexplore.exeshellopencommand
    HKEY_CLASSES_ROOTftpshellopencommand
    HKEY_LOCAL_MACHINESOFTWAREClassesApplicationsiexplore.exe
    shellopencommand
    HKEY_LOCAL_MACHINESOFTWAREClassesftpshellopencommand
    
    
15. In the right pane, delete any reference to iexplore.com.
    
    
16. Navigate to the key:
    
    HKEY_CLASSES_ROOThttpshellopencommand
    
    
17. In the right pane delete any reference to iexplore.pif.
    
    
18. Navigate to the key:
    
    HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain
    
    
19. Change the following value:
    
    "Check_Associations" = "yes"
    
    if applicable.
    
    
20. Navigate to and delete the following subkeys:
    
    HKEY_CLASSES_ROOTCLSID{871C5380-42A0-1069-A2EA-08002B30309D
    }shellOpenHomePageCommand
    HKEY_LOCAL_MACHINESOFTWAREClassesCLSID
    {871C5380-42A0-1069-A2EA-08002B30309D}shellOpenHomePageCommand
    
    
21. Exit the Registry Editor.