Trojan.Gletta.A

SUMMARY

Trojan.Gletta.A is a Trojan horse that steals Internet banking passwords. It logs keystrokes when you visit certain Web pages and emails the log to the attacker.

Web pages that link to .CHM files to exploit the Microsoft Internet Explorer ITS Protocol Zone Bypass Vulnerability are known to distribute Trojan.Gletta.A.

Protection

• Virus Definitions (LiveUpdate™ Weekly) June 9, 2004
• Virus Definitions (Intelligent Updater) June 9, 2004

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: Medium
• Modifies Files: May modify the SYSTEM.INI and WIN.INI files.
• Releases Confidential Info: Captures keystrokes from Internet banking Web sites.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Trojan.Gletta.A executes, it does the following:

1. Copies itself to:
   • %System%Wmiprvse.exe
   • %System%Ntsvc.exe
   • %Windir%Userlogon.exe
     
     

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     Notes:
     %System% is a variable. Trojan.Gletta.A 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).
     
     %Windir% is a variable. The Trojan.Gletta.A locates the Windows installation folder (by default, this is C:Windows or C:Winnt) and copies itself to that location.

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2. Creates the file, %System%Rsasec.dll, which is a keylogger.
   
   
3. Creates the file, %System%sacb.dll, which is actually a text file.
   
   
4. Adds the value:
   
   "wmiprvse.exe"="%system%wmiprvse.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsCurrentVersionRun
   
   so that the Trojan runs when you start Windows.
   
   
5. On Windows NT/2000/XP, it adds the value:
   
   "Run" = "%Windir%userlogon.exe"
   
   to the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWindows
   
   so that the Trojan runs when you start these operating systems.
   
   
6. On Windows 95/98/Me, it adds the line:
   
   run=%Windir%userlogon.exe
   
   to the Win.ini file so that the Trojan runs when you start these operating systems.
   
   
7. On Windows 95/98/Me, it changes the shell= line to:
   
   shell=explorer.exe %system% tsvc.exe
   
   so that the Trojan runs when you start these operating systems.
   
   
8. Watches for Internet Explorer windows that have any of the following titles:
   
   National Australia Bank
   ANZ Internet Banking - Logon
   National Internet Banking
   Citibank Australia
   Welcome to Citi
   Welcome to Citibank
   Citi - Sign On
   Bank of China
   online@hsbc
   HSBC in Hong Kong
   Banesto
   Sabadell
   
   or one of the following URLs:
   
   https:/ /olb.westpac.com.au/ib/asp/
   https:/ /olb.westpac.com.au/ib/
   
   
9. Captures all the keystrokes entered into any windows that match those listed above, and writes them into a log file.
   
   
10. Uses its own SMTP engine to send the log file to an external mail account. It uses an SMTP server in Russia to send the mail.
    
    The mail has the following characteristics:
    
    Both the FROM and TO addresses have the domain "mail.ru"
    The subject starts with "Business News from "
    

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. Restart the computer in Safe mode or VGA Mode.
4. Run a full system scan and delete all the files detected as Trojan.Gletta.A.
5. Delete the value that was added to the registry.
6. Edit the Win.ini file.
7. Edit the System.ini file.
   

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"

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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.

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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 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. 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 Trojan.Gletta.A, click Delete.
   

5. To delete the value from the registry

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WARNING: 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.

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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 value:
   
   "wmiprvse.exe" = "%system%wmiprvse.exe"
   
   
5. Do one of the following:
   • Windows 95/98/Me. Skip to step h.
   • Windows NT/2000/XP. Proceed with step f.
     
     
6. Navigate to the key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWindows
   
   
7. In the right pane, delete the value:
   
   "Run" = "%windir%userlogon.exe"
   
   
8. Exit the Registry Editor.
9. Do one of the following:
   • Windows 95/98/Me. Proceed with section 6.
   • Windows NT/2000/XP. You are finished with the removal. Restart the computer in normal mode.
     

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

• 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 file that you need to edit. If this backup copy exists, 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.
       
       

1. Click Start, and then click Run.
2. 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.
   
   
3. In the [windows] section of the file, look for a line similar to:
   
   [windows] run=%Windir%userlogon.exe
   
   
4. If this line exists, delete it.
5. Click File, and then click Save.
6. Click File, and then click Exit.
   
   

7. Edit the System.ini file
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 System.ini file that you need to edit. If this backup copy exists, 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 System.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:windowssystem.ini
   
   (The MS-DOS Editor opens.)
   
   NOTE: If Windows is installed in a different location, make the appropriate path substitution.
   
   
4. In the [boot] section of the file, look for a line similar to:
   
   [boot] shell=explorer.exe %system% tsvc.exe
   
   
5. If this line exists, delete everything to the right of Explorer.exe.
   
   When you are done, it should look like:
   
   [boot] shell=Explorer.exe
   
   
6. Click File, and then click Save.
7. Click File, and then click Exit.