Backdoor.Prorat

SUMMARY

Backdoor.Prorat:

• Is a Backdoor Trojan horse that gives an attacker full control over your computer.
• Opens a port on the system.
• Is written in Delphi.
• Is packed with UPX.

Protection

• Virus Definitions (LiveUpdate™ Weekly) June 18, 2003
• Virus Definitions (Intelligent Updater) June 13, 2003

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
• Compromises Security Settings: Allows unauthorized remote access to an infected computer.

Distribution

• Distribution Level: Low
• Ports: 58343

TECHNICAL DETAILS

When Backdoor.Prorat is executed, it performs the following actions:

1. Copies itself to the %System% or %Windir% folder. The following file names have been seen, however, it is possible that different variants use different file names:
   • %System%Main.exe
   • %System%Loader.exe
   • %System%Msmsg.exe
   • %System%Winserv.dll
   • %System%Fservice.exe
   • %System%Sservice.exe
   • %Windir%Winlogon.exe
     
     Notes:
     • %Windir% is a variable. The Backdoor.Prorat 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 Backdoor.Prorat 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).
       
       
2. Creates .dll files in the %System% folder. The following file names have been seen, however, it is possible that different variants use different file names:
   • %System%wininv.dll
   • %System%winkey.dll
     
     
3. Adds a value at one or more of the following locations in the Windows registry:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   PoliciesExplorerRun
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftActive SetupInstalled Components{5Y99AE78-58TT-11dW-BE53-Y67078979Y}
   
   HKEY_CURRENT_USERSOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
   The following values have been seen added:
   
   "MSNMESENGER"="%System%Main.exe"
   
   "DirectX for Microsoft Windows"="%System%Fservice.exe"
   
   "DirectX for Microsoft Windows"="%System%Sservice.exe"
   
   "StubPath"="C:WindowssystemSservice.exe"
   
   
4. Modifies the value data of:
   
   Shell
   
   in the registry key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWinlogon
   
   from:
   
   "explorer.exe"
   
   to:
   
   "explorer.exe %System%Fservice.exe"
   
   so that the backdoor runs when you start Windows NT/2000/XP.
   
   
5. Opens a listening port. All the variants seen so far open a port in the range of 50000 - 60000.
   
   
6. Sends the version number of the Trojan, as well as the IP address and port number of the target computer, to a specific ICQ user through the ICQ Web pager.
   
   
7. May inject a .dll file into the Winlogon process as a thread, which will end the processes of various security products.

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 (Windows 95/98/Me) or Safe mode with Command Prompt (Windows 2000/XP).
4. Reverse the changes made to the registry.
5. Restart the computer in Safe mode or VGA mode (Windows Me/XP).
6. Run a full system scan and delete all the files detected as Backdoor.Prorat.
   

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"

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 Safe mode with Command Prompt
Follow the instructions for your operating system.

Windows 95/98/Me
Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."

Once in Safe mode (this could take some time), proceed with section 4.

Windows 2000

1. Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer.
2. When you see the black and white Starting Windows bar at the bottom of the screen, press the F8 key (usually on the top row of the keyboard).
3. In the Windows 2000 Advanced Options Menu, select Safe mode with Command Prompt, and then press Enter.
   
   Once the computer opens to a window with a command prompt (you should see a line of text and a blinking cursor), proceed with section 4.

Windows XP

1. Shut down the computer and turn off the power. Wait for at least 30 seconds, and then restart the computer. The computer begins processing a set of instructions known as the Basic Input/Output System (BIOS). What is displayed depends on the BIOS manufacturer. Some computers display a progress bar that refers to the word BIOS, while others may not display any indication that this process is occurring.
2. As soon as the BIOS has finished loading, begin tapping the F8 key on your keyboard. Continue to do so until the Windows Advanced Options menu appears. If you begin tapping the F8 key too soon, some computers will display a "keyboard error" message. To avoid this, restart the computer and try again.
3. In the Windows 2000 Advanced Options Menu, select Safe mode with Command Prompt, and then press Enter.
   
   Once the computer opens to a window with a command prompt (you should see a line of text and a blinking cursor), proceed with section 4.

4. To reverse the changes made to 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. Do one of the following:
   • Windows 2000/XP. Skip to step b.
   • Windows 95/98/Me. Click Start > Run.
     
     
2. Type the following:
   
   regedit
   
   
3. Do one of the following:
   • Windows 2000/XP: Press Enter.
   • Windows 95/98/Me: Click OK.
     
     
4. Navigate to each of these keys:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersion
   PoliciesExplorerRun
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftActive SetupInstalled Components{5Y99AE78-58TT-11dW-BE53-Y67078979Y}
   
   HKEY_CURRENT_USERSOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
5. For each one, in the right pane, if any of the following values are found, delete that value:
   
   "MSNMESENGER"="%System%Main.exe"
   
   "DirectX for Microsoft Windows"="%System%Fservice.exe"
   
   "DirectX for Microsoft Windows"="%System%Sservice.exe"
   
   "StubPath"="C:WindowssystemSservice.exe"
   
   
6. Do one of the following:
   • Windows 95/98/Me. Skip to step i.
   • Windows NT/2000/XP: Proceed with step g.
     
     
7. Navigate to the key:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftWindows NTCurrentVersionWinlogon
   
   
8. In the right pane, modify the value:
   
   "Shell"="explorer.exe %System%Fservice.exe"
   
   to:
   
   "Shell"="explorer.exe"
   
   
9. Exit the Registry Editor.
   
10. Do one of the following:
    • Windows 95/98/Me: Skip to section 6.
    • Windows NT/2000/XP: Continue on to section 5.
      
      

5. 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.
• In Windows 95, 98, Me, 2000, or XP, restart the computer in Safe mode.
  For instructions, read the document "How to start the computer in Safe Mode."
• In Windows NT 4, restart the computer in VGA mode.
  

6. 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 Backdoor.Prorat, click Delete.