Trojan.Gaslide

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Discovered: August 26, 2003
Updated: February 13, 2007 12:05:32 PM
Type: Trojan Horse
Systems Affected: Windows


Trojan.Gaslide is a Trojan Horse that attempts to modify the settings in the Internet Explorer Web browser.

Antivirus Protection Dates

  • Initial Rapid Release version August 27, 2003
  • Latest Rapid Release version August 08, 2016 revision 023
  • Initial Daily Certified version August 27, 2003
  • Latest Daily Certified version August 09, 2016 revision 001
  • Initial Weekly Certified release date August 27, 2003

Click here for a more detailed description of Rapid Release and Daily Certified virus definitions.

Writeup By: Scott Gettis

Discovered: August 26, 2003
Updated: February 13, 2007 12:05:32 PM
Type: Trojan Horse
Systems Affected: Windows


When Trojan.Gaslide is executed, it does the following:

  1. Copies itself to the local disk and drops files in various locations. There are several variants of this Trojan; they differ mainly in the location of the dropped files. The description below applies to two variants that Symantec Security Response received, but other variations are possible.
    • File locations for Variant 1:
      • C:\Cdrunxp.exe: A copy of the Trojan
      • C:\Mscomctl.vxd: A copy of the Trojan
      • C:\Gsupx.exe: (*) A UPX-packed version of the UPX packer
      • C:\Notepad32.exe: (*) A UPX-packed version of Notepad
      • C:\Notepad.exe: A Microsoft Visual Basic Program that modifies the registry
      • C:\NLoad.vxd: (*) A UPX-packed version of Notepad
      • C:\Helpctl.exe: A Microsoft Visual Basic Program that modifies the registry and loads the Trojan
      • C:\Iexplorer.exe: (*) This file modifies settings in the Internet Explorer Web browser

        The files marked with (*) are not malicious, and thus, Symantec antivirus products do not detect them.

    • File locations for Variant 2:
      • %System%\Cdrunxp.exe: A copy of the Trojan
      • %System%\Notepad.exe: A Microsoft Visual Basic Program that modifies the registry
      • %System%\Notepad32.exe: (*) A UPX-packed version of Notepad
      • %Windir%\Notepad.exe: A UPX-packed version of the Trojan file %System%\Notepad.exe
      • %Windir%\Notepad32.exe: (*) A UPX-packed version of Notepad
      • %Windir%\Iexplorer.exe: (*) This file modifies settings in the Internet Explorer Web browser
      • %Temp%\Gsupx.exe: (*) A UPX-packed version of the UPX packer
      • %Temp%\Helpctl.exe: A Microsoft Visual Basic Program that modifies the registry and loads the Trojan
      • %Temp%\Mscomctl.vxd: A copy of the Trojan
      • %Temp%\NLoad.vxd: A Microsoft Visual Basic Program that modifies the registry
      • %System%\Restore\Rstrui.exe: A copy of the Trojan

        The files marked with (*) are not malicious, and thus, Symantec antivirus products do not detect them.

  2. May also create, and later delete, temporary files that have a .gst extension.

  3. Modifies the default value of the following registry key:

    HKEY_CLASSES_ROOT\exefile\shell\open\command

    This causes the Trojan to execute every time a .exe file is executed.

  4. May add the values:

    "<path>\helpctl.exe" = "<path>\helpctl.exe"
    "slide" = "Iexplore.exe"

    to one or both of the registry keys:

    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

  5. May reset the default Internet Explorer home page to a pornographic Web site.


Recommendations

Symantec Security Response encourages all users and administrators to adhere to the following basic security "best practices":

  • Use a firewall to block all incoming connections from the Internet to services that should not be publicly available. By default, you should deny all incoming connections and only allow services you explicitly want to offer to the outside world.
  • 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.
  • Ensure that programs and users of the computer use the lowest level of privileges necessary to complete a task. When prompted for a root or UAC password, ensure that the program asking for administration-level access is a legitimate application.
  • Disable AutoPlay to prevent the automatic launching of executable files on network and removable drives, and disconnect the drives when not required. If write access is not required, enable read-only mode if the option is available.
  • Turn off file sharing if not needed. If file sharing is required, use ACLs and password protection to limit access. Disable anonymous access to shared folders. Grant access only to user accounts with strong passwords to folders that must be shared.
  • Turn off and remove unnecessary services. By default, many operating systems install auxiliary services that are not critical. These services are avenues of attack. If they are removed, threats have less avenues of attack.
  • If a 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.
  • Configure your email server to block or remove email that contains file attachments that are commonly used to spread threats, such as .vbs, .bat, .exe, .pif and .scr files.
  • Isolate compromised computers quickly to prevent threats from spreading further. 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.
  • If Bluetooth is not required for mobile devices, it should be turned off. If you require its use, ensure that the device's visibility is set to "Hidden" so that it cannot be scanned by other Bluetooth devices. If device pairing must be used, ensure that all devices are set to "Unauthorized", requiring authorization for each connection request. Do not accept applications that are unsigned or sent from unknown sources.
  • For further information on the terms used in this document, please refer to the Security Response glossary.

Writeup By: Scott Gettis

Discovered: August 26, 2003
Updated: February 13, 2007 12:05:32 PM
Type: Trojan Horse
Systems Affected: Windows



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.Gaslide.
  4. Reverse the changes that were made to the registry.
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:
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.
  2. Run a full system scan.
  3. If any files are detected as Trojan.Gaslide, click Delete.
  4. If necessary, replace %Windir%\Notepad.exe with a backup copy.

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. (The Run dialog box appears.)
  2. Type regedit

    Then click OK. (The Registry Editor opens.)

  3. Navigate to each of the following keys:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
    HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run

  4. In the right pane, delete any values referring to the Trojan.

  5. Navigate to the registry key:

    HKEY_CLASSES_ROOT\exefile\shell\open\command

  6. In the right pane, change the default value to: "%1" %*

  7. Exit the Registry Editor.


Writeup By: Scott Gettis