W32.HLLW.Caspid

SUMMARY

W32.HLLW.Caspid is a worm that spreads through file-sharing networks, such as Morpheus and KaZaA. It is a virus that infects HTML files. This worm may also spread through email by setting itself as the default stationery used in email messages.

W32.HLLW.Caspid takes advantage of a vulnerability described in MS03-14, which allows for the execution of a MIME-encoded program inside an HTML file.

This worm is written in Visual Basic and is packed with UPX.

The existence of %Windir%Capside.exe or %Windir%Capside.htm is an indication of infection.

Protection

• Virus Definitions (LiveUpdate™ Weekly) September 11, 2003
• Virus Definitions (Intelligent Updater) September 11, 2003

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: Medium
• Payload: May be inserted into new email messages that the user of an infected system created.
• Modifies Files: Infects all the HTML files.

Distribution

• Distribution Level: Medium
• Target of Infection: Shared directories that various file-sharing programs uses.

TECHNICAL DETAILS

W32.HLLW.Caspid performs the following actions:

1. The first time this worm executes, it displays a message box containing the text "Por Cristo he sido salvado:"
   
   
   
   
   
2. Copies itself as:
   • %Windir%Capside.exe
   • %Windir%CapsideRed.pif
   • %System%<random filename>.scr
     
     

     ---

     Notes:
     %Windir% is a variable. The worm 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 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).
     

     ---

     
     
3. Creates the following html files, which contain a MIME-encoded copy of the executable:
   • %Windir%Capside.htm
   • %Windir%CapsideCode.htm
   • %CommonProgramFiles%Microsoft SharedStationeryCapside.htm
     
     
4. Adds the value:
   
   "W32Load"="%System%<random filename>.scr"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that the worm runs when you start Windows.
   
   
5. Modifies the Win.ini file as follows:
   
   [windows]
   run=%Windows%CapsideRed.pif
   
   NOTE: %Windows% is a variable. The worm locates the Windows installation folder (by default, this is C:Windows or C:Winnt) and copies itself to that location.
   
   
6. Modifies the System.ini file as follows:
   
   [boot]
   shell=Explorer.exe %Windows%Capside.exe
   
   
7. Attempts to set itself as the default stationery that is used to create email messages. It does this by modifying registry keys as follows:
   
   • Sets the values:
     
     Stationery Name = "%Windows%Capside.htm"
     Wide Stationery Name = "%Windows%Capside.htm"
     
     in the registry key:
     
     HKEY_CURRENT_USERIdentities[Default Use ID]SoftwareMicrosoftOutlook Express[Outlook Version].0Mail
     
     
   • Sets the value:
     
     NewStationery = Capside
     
     in the registry key:
     
     HKEY_CURRENT_USERSoftwareMicrosoftOffice[Version].0CommonMailSettings
     
     
   • Sets the value:
     
     001e0360 = Capside
     
     in the registry keys:
     
     HKEY_CURRENT_USERSoftwareMicrosoftWindows Messaging SubsystemProfilesMicrosoft Outlooka0d020000000000c000000000000046
     HKEY_CURRENT_USERSoftwareMicrosoftWindows Messaging SubsystemProfilesMicrosoft Outlook Internet Settingsa0d020000000000c000000000000046
     HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersion
     Windows Messaging SubsystemProfilesMicrosoft Outlooka0d020000000000c000000000000046
     HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersion
     Windows Messaging SubsystemProfilesMicrosoft Outlook Internet Settingsa0d020000000000c000000000000046
     
     
8. Spreads through file-sharing networks by copying itself in encoded HTML form to the shared folders, which the following applications use:
   
   • BearShare
   • eDonkey
   • ICQ
   • Filetopia
   • FileNavigator
   • Gnucleus
   • Grokster
   • iMesh
   • Kazaa
   • Morpheus
   • LimeWire
   • Overnet
   • Soulseek
     
     
     And to the hard-coded path:
     
     
   • C:My Downloads
     
     it uses the following filenames:
     
     
   • ACDSee 5.5.html
   • Age of Empires 2 crack.html
   • Ana Kournikova Sex Video.html
   • Animated Screen 7.0b.html
   • aol cracker.html
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9. Searches the Windows folder for any file that has an htm or html extension, recursively processing subfolders. The worm infects every such file it finds, encrypting the host file and infecting it with an encoded version of the worm executable.

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 as W32.HLLW.Caspid.
4. Reverse the modifications made to the registry.
5. Edit the system files.
   

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.HLLW.Darby, click Delete.

4. Reversing the changes made to 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.
   
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 value:
   
   "W32Load"="%System%<random filename>"
   
   
5. Exit the Registry Editor.

5. Editing the system files

If you are running Windows 95/98/Me, follow these steps:

1. The function you perform depends on your operating system:
   • Windows 95/98: Go to step B.
   • Windows Me: If you are running Windows Me, the Windows Me file-protection process may have made a backup copy of the Win.ini and System.ini files that you need to edit. If these backup copies exist, it will be in the C:WindowsRecent folder. Symantec recommends that you delete this file before continuing with the steps in this section. To do this:
     1. Start Windows Explorer.
     2. Browse to and select the C:WindowsRecent folder.
     3. In the right pane, select the Win.ini file and delete it. The Win.ini file will be regenerated when you save your changes to it in step F.
        
        
2. Click Start, and then click Run.
3. Type the following, and then click OK.
   
   edit c:windowswin.ini
   
   (The MS-DOS Editor opens.)
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
   
4. In the [windows] section of the file, look for a line similar to:
   
   run = C:WINDOWSCapsideRed.pif
   
   If this line exists, delete it.
   
   
5. Click File, and then click Save.
6. Click File, and then click Close.
7. Click File, and then click Open.
8. Type the following and then click OK:
   
   c:windowssystem.ini
   
   
9. In the [boot] section of the file, look for a line similar to:
   
   shell = Explorer.exe C:WINDOWSCapside.exe
   
   
10. If this line exists, delete everything to the right of Explorer.exe.
    
    When you are done, it should look like:
    
    shell = Explorer.exe
    
    
11. Click File, and then click Save
12. Click File, and then click Exit.