W32.Sachiel

SUMMARY

W32.Sachiel is a virus that attempts to spread itself through the floppy disk drive. It is written in the Microsoft Visual Basic programming language and is compressed with UPX. The size of this virus is approximately 45 KB after it is decompressed.

Protection

• Virus Definitions (LiveUpdate™ Weekly) June 19, 2002
• Virus Definitions (Intelligent Updater) June 17, 2002

Threat Assessment

Wild

• Wild Level: Low
• Number of Infections: 50 - 999
• Number of Sites: More than 10
• Geographical Distribution: Low
• Threat Containment: Easy
• Removal: Moderate

Damage

• Damage Level: Low
• Deletes Files: Files that have .pwl as an extension name

Distribution

• Distribution Level: Low
• Shared Drives: Copies itself to the floppy drive

TECHNICAL DETAILS

When W32.Sachiel runs, it does the following:

1. Displays the following message:
   
   
   
   
2. Copies itself as:
   • %Windir%HelpSachiel.sys.bat
   • %System%Helpdks.dll
   • %System%Winrun.sys.pif
     
     The file attributes are set to Hidden and System.
     
     NOTES:
     • %Windir% is a variable. The virus locates the Windows installation folder (by default, this is C:Windows or C:Winnt) and copies itself to that location.
     • %System% is a variable. The virus 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).
       
       
3. Attempts to copy itself to the floppy disk as one of the following:
   • Marittsa.jpg.scr
   • 3rimpact.bat
   • VidaMia.jpg.scr
   • Informes.txt.pif
   • Ovnis45.jpg.scr
     
     
4. Searches for files with the .gif, .htm, or .html extension in all the folders of all the drives, except for the root folders. If the virus finds a file, it makes a copy of itself using the same filename and an extra extension of .pif.
   
   For example, if the file C:Program FilesTestGoat.gif exists, the virus copies itself as C:Program FilesTestGoat.gif.pif.
   
   
5. Searches for the files with the .jpg or .jpeg extension in all the folders of all the drives, except for the root folders. If the virus finds a file, it makes a copy of itself using the same filename and an extra extension of .scr.
   
   
6. Deletes any files that have .pwl as an extension name in all the folders of all the drives, except for the root folders.
   
   
7. Adds the values:
   
   "Thsys"="%windir%helpSachiel.sys.bat"
   "Mmsystem"="%system%winrun.sys.pif"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that the virus runs each time you start Windows.
   
   
8. Adds the value, Soundir, to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   
   
9. Modifies the win.ini file as follows:
   
   [Windows]
   run=%system%winrun.sys.pifs
   
   so that the virus runs when you start Window 95/98/Me.
   
   
10. Deletes the following files from the system:
    • %Windir%Regedit.exe
    • %System%Msconfig.exe
    • %System%Sfc.exe.exe
    • %System%Sysedit.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

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.
3. Run a full system scan and delete all the files detected as W32.Sachiel.
4. Restore the deleted system files.
5. Delete the values that were added to the registry.
   

For specific 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
All the Windows 32-bit operating systems, except Windows NT, can be restarted in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."

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.Sachiel, click Delete.

4. Restoring the deleted system files
If any of the following files were deleted, restore them from a clean backup or re-install them.

• %Windir%Regedit.exe
• %System%Msconfig.exe
• %System%Sfc.exe.exe
• %System%Sysedit.exe

5. Deleting the value from the registry

CAUTION: 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.

1. Click Start, and then click Run. (The Run dialog box appears.)
2. Type regedit
   
   Then click OK. (The Registry Editor opens.)
   
   
3. Navigate to the key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
4. In the right pane, delete the values:
   
   "Thsys"="%windir%helpSachiel.sys.bat"
   "Mmsystem"="%system%winrun.sys.pif"
   
   
5. Navigate to the key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   
   
6. In the right pane, delete the value: Soundir
   
   
7. Exit the Registry Editor.