Trojan.Adwareloader

SUMMARY

Trojan.Adwareloader is a Trojan horse program that lowers Windows security settings and downloads adware and spyware.

Protection

• Virus Definitions (LiveUpdate™ Weekly) March 16, 2005
• Virus Definitions (Intelligent Updater) March 14, 2005

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: Low
• Payload: Downloads adware and spyware.
• Compromises Security Settings: Disables various security features in Windows.

Distribution

• Distribution Level: Low

TECHNICAL DETAILS

When Trojan.Adwareloader is executed, it performs the following actions:

1. Creates the mutex SouthPark, so that only one instance of the Trojan will run on the compromised computer.
   
   
2. Creates the following copies of itself:
   
   
   • %System%[Trojan file name]
   • %System%msoffice.exe
     
     Note: %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).
     
     
3. Adds the value:
   
   "WebRun" = "%System%[Trojan file name]"
   
   to the registry subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   so that it is executed every time Windows starts.
   
   
4. Adds the value:
   
   "run" = "%System%msoffice.exe"
   
   to the registry subkey:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersionWindows
   
   so that it is executed every time Windows starts.
   
   
5. Adds the following line to the [Windows] section of the Win.ini file, on computers running Windows 95/98:
   
   run = %System%msoffice.exe
   
   
6. Downloads several adware and spyware files from the private-admin.biz domain.
   
   
7. Downloads the file commands.ini from the private-admin.biz domain. This is an encrypted file that contains information on registry keys to be set.
   
   
8. Adds the value:
   
   "Cartman" = "[DWORD Value]"
   
   to the registry subkeys:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerMain
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain
   
   where [DWORD Value] is taken from the commands.ini file, and serves as a version number.
   
   
9. Modifies the following registry entry based on the contents of the commands.ini file:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftInternet ExplorerMainStart Page
   
   This results in the Internet Explorer start pages being redirected.
   
   
10. Adds the following values:
    
    "FirewallDisableNotify" = "1"
    "UpdatesDisableNotify" = "1"
    "AntiVirusDisableNotify" = "1"
    
    to the registry subkeys:
    
    HKEY_LOCAL_MACHINESOFTWAREMicrosoftSecurity Center
    HKEY_CURRENT_USERSOFTWAREMicrosoftSecurity Center
    
    to disable several security features in Windows.
    
    
11. Adds the following values:
    
    "NoAutoUpdate" = "1"
    "AUOptions" = "1"
    
    to the registry subkeys:
    
    HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoftWindowsWindowsUpdateAU
    HKEY_CURRENT_USERSOFTWAREPoliciesMicrosoftWindowsWindowsUpdateAU
    
    to disable several security features in Windows.
    
    
12. Adds the following value:
    
    "EnableFirewall" = "1"
    
    to the registry subkeys:
    
    HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoftWindowsFirewallStandardProfile
    HKEY_LOCAL_MACHINESOFTWAREPoliciesMicrosoftWindowsFirewallDomainProfile
    HKEY_CURRENT_USERSOFTWAREPoliciesMicrosoftWindowsFirewallStandardProfile
    HKEY_CURRENT_USERSOFTWAREPoliciesMicrosoftWindowsFirewallDomainProfile
    
    to disable several security features in Windows.

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 Trojan.Adwareloader.
4. Delete the value that was added to the registry.
5. Edit the Win.ini file.
6. To reset the Internet Explorer home page.
7. To restore the Windows Security Center.
   

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 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.Adwareloader, 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.
   

4. 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 subkeys:
   
   HKEY_LOCAL_MACHINESoftwareMicrosoftInternet ExplorerMain
   HKEY_CURRENT_USERSoftwareMicrosoftInternet ExplorerMain
   
   
4. In the right pane, delete the value:
   
   "Cartman" = "[DWORD Value]"
   
   
5. Navigate to the subkey:
   
   HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun
   
   
6. In the right pane, delete the value:
   
   "WebRun" = "%System%[Trojan file name]"
   
   
7. Navigate to the subkey:
   
   HKEY_CURRENT_USERSoftwareMicrosoftWindows NTCurrentVersionWindows
   
   
8. In the right pane, delete the value:
   
   "run" = "%System%msoffice.exe"
   
   
9. Exit the Registry Editor.

5. 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 = %System%msoffice.exe
   
   
4. If this line exists, delete everything to the right of run=
   
   
5. Click File > Save.
6. Click File > Exit.
   

6. 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.


7. To restore the Windows Security Center
This threat attempts to disable the features in the Windows Security Center, available in Windows XP Service Pack 2. If you are running Windows XP Service Pack 2 and would like to restore the full functionality of the Windows Security Center, please complete the following steps:

Important: If your computer is connected to a domain, you may not be able to adjust these settings. If so, contact your network administrator for more information.

1. Click Start > Control Panel.
2. Double-click the Security Center.
3. In the right pane, click Windows Firewall. The Windows Firewall appears.
4. Select On.
5. Click OK to close the Windows Firewall.
6. In the left pane of the Security Center, select Change the way Security Center alerts me.
7. Click Alert Settings.
8. Select Alert Settings, Firewall, and Virus Protection.
9. Click OK
10. Click Automatic Updates.
11. Select Automatic.
12. Click OK.
13. Exit the Security Center.