W32.Holcas.A@mm

SUMMARY

W32.Holcas.A@mm is a mass-mailing worm that uses MAPI commands to send itself to all addresses found in the Windows Address Book. It also attempts to send itself via IRC.

The email has the following characteristics:

Subject: hola como estas, ;o)
Attachment: Que_entretenido.exe

Protection

• Virus Definitions (LiveUpdate™ Weekly) March 2, 2005
• Virus Definitions (Intelligent Updater) February 28, 2005

Threat Assessment

Wild

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

Damage

• Damage Level: Low

Distribution

• Distribution Level: High
• Subject of Email: hola como estas, ;o)
• Name of Attachment: Que_entretenido.exe
• Size of Attachment: 107,520 bytes

TECHNICAL DETAILS

When W32.Holcas.A@mm is executed, it performs the following actions:

1. Creates the following copies of itself:
   
   
   • %System%emotehost.pif
   • %Windir%Autoexec.com
   • C:Contraseñas.exe
   • C:Start.exe
   • C:WindowsQue_entretenido.exe
   • C:Windowsuntime32.exe
   • C:autoexec.pif
     
     Notes:
   • %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).
     
     
2. Creates the following additional files:
   
   
   • C:agente.vbs
   • C:DemonViriViene.txt (A non-malicious text file.)
   • C:script.ini
     
     
3. Attempts to copy itself to the root of drives A through Z under the following conditions:
   
   • If the drive type is removable, the worm copies itself to that drive as Fondo.exe.
   • If the drive type is ramdisk, the worm copies itself to that drive as virusram.exe.
   • If the drive type is CDROM, the worm copies itself to that drive as Play.exe.
   • If the drive type is fixed, the worm copies itself to that drive as Claves.exe.
   • If the drive type is remote, the worm copies itself to that drive as Server.exe.
   • If the drive type is unknown, the worm copies itself to that drive as Y_Fenix.com.
     
     
4. Continuously attempts to copy itself as A:soccer.exe.
   
   
5. Adds the value:
   
   "Sistray32" = "%System%emotehost.pif"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that the worm runs every time Windows starts.
   
   
6. On Windows 95/98/Me, adds the following line in the [Windows] section of the win.ini file
   
   run=%Windir%Autoexec.com
   
   so that the worm runs every time Windows starts.
   
   
7. Adds the following to the file autoexec.bat:
   
   @C:autoexec.pif
   
   
8. On Windows NT/2000/XP, adds the value:
   
   "run" = "%Windir%Autoexec.com"
   
   to the registry subkey:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersionWindows
   
   so that the worm runs every time Windows starts.
   
   
9. Launches C:agente.vbs, which performs the mass-mailing routine by using MAPI commands to send the following email to all contacts in the Windows Address Book:
   
   Subject: hola como estas, ;o)
   
   Message: Con Cariño:
   
   Attachment: Que_entretenido.exe
   
   
10. Sends itself to other IRC users as the file C:Contraseñas.exe, based on the contents of C:script.ini.
    
    
11. Hides the Windows Taskbar.
    
    
12. Adds the value:
    
    "Start Page"="http:/ /viricototal.tk"
    
    to the registry key:
    
    HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain
    
    
13. Creates the value:
    
    "Pseudoroot" = "Mujpider"
    
    in the registry key:
    
    HKEY_CURRENT_USERSoftwareViricoTotalTeam
    
    as an infection marker.

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. To restart the computer in Safe mode.
4. Run a full system scan and delete all the files detected as W32.Holcas.A@mm.
5. Delete the value that was added to the registry.
6. Edit the Win.ini file.
7. Edit the Autoexec.bat file.
8. Reset the Internet Explorer home page.
   

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, re-enable 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 the 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 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. To restart 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.

4. 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 as infected with W32.Holcas.A@mm, click Delete.
   
   Note: If your Symantec antivirus product reports that it cannot delete an infected file, Windows may be using the file. To fix 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 section 4.
   

5. 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. Read the document, "How to make a backup of the Windows registry," for instructions.

1. Click Start > Run.
2. Type regedit
   
   Then click OK.
   
   
3. Navigate to the subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
4. In the right pane, delete the value:
   
   "Sistray32" = "%System%emotehost.pif"
   
   
5. Navigate to the subkey:
   
   HKEY_CURRENT_USERSOFTWAREMicrosoftWindows NTCurrentVersionWindows
   
   
6. In the right pane, delete the value:
   
   "run" = "%Windir%Autoexec.com"
   
   
7. Navigate to the subkey:
   
   HKEY_CURRENT_USERSOFTWARE
   
8. In the left pane, delete the subkey:
   
   ViricoTotalTeam
   
   
9. Exit the Registry Editor.

6. Edit the Win.ini file
If you are running Windows 95/98/Me, follow these steps:

1. Click Start > Run.
2. Type the following:
   
   edit c:windowswin.ini
   
   and then click OK.
   
   (The MS-DOS Editor opens.)
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
   
3. In the [windows] section of the file, look for a line similar to:
   
   run=%Windir%Autoexec.com
   
   
4. If this line exists, delete everything to the right of run=
   
   
5. Click File > Save.
6. Click File > Exit.

7. Edit the Autoexec.bat file
If you are running Windows 95/98/Me, follow these steps:

1. Click Start > Run.
2. Type the following:
   
   edit c:autoexec.bat
   
   and then click OK.
   
   (The MS-DOS Editor opens.)
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
   
3. Look for a line similar to:
   
   @C:autoexec.pif
   
   
4. If this line exists, delete it.
   
5. Click File > Save.
6. Click File > Exit.

8. To reset the Internet Explorer home page

1. Start Microsoft Internet Explorer.
2. Connect to the Internet, and then go to the page that you want to set as your home page.
3. Click Tools > Internet Options.
4. In the Home page section of the General tab, click Use Current > OK.

For additional information, or if this procedure does not work, read the Microsoft® Knowledge Base article, "Home Page Setting Changes Unexpectedly, or You Cannot Change Your Home Page Setting, Article ID 320159."