Backdoor.AntiLam.20.K

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Discovered: May 02, 2003
Updated: February 13, 2007 12:00:46 PM
Type: Trojan Horse
Systems Affected: Windows


Backdoor.AntiLam.20.K is a Backdoor Trojan Horse that gives a hacker access to your computer.

Antivirus Protection Dates

  • Initial Rapid Release version May 05, 2003
  • Latest Rapid Release version March 03, 2008 revision 035
  • Initial Daily Certified version May 05, 2003
  • Latest Daily Certified version March 03, 2008 revision 037
  • Initial Weekly Certified release date May 07, 2003

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

Writeup By: Heather Shannon

Discovered: May 02, 2003
Updated: February 13, 2007 12:00:46 PM
Type: Trojan Horse
Systems Affected: Windows


Backdoor.AntiLam.20.K is a minor variant of Backdoor.AntiLam.20 . It makes some additional modifications to system files.

When Backdoor.AntiLam.20.K is executed, it does the following:

  1. Copies itself as %System%\internat.exe and attempts to delete the original Trojan file.

    NOTE: %System% is a variable: The Trojan locates the System folder and copies itself to that location. By default, this is C:\Windows\System (Windows 95/98/Me), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

  2. Creates the file, %System%\Scan.dll, which Symantec antivirus products detect as PWS.Hooker.Trojan.

  3. If the operating system is Windows 95/98/Me, it makes the following modifications so that it runs when you start Windows:
    • Modifies the shell= line of the [boot] section of the System.ini file to:

      shell=Explorer.exe C:\WINDOWS\SYSTEM\internat.exe
    • Adds the line:

      run=C:\WINDOWS\SYSTEM\internat.exe

      to the [windows] section of the Win.ini file.

  4. Adds the value:

    "SVCHOST"="%System%\internat.exe"

    to the following keys:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

    so that the Trojan runs when you start Windows.

  5. Creates the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\KeyConfig

    which contains the configuration information of the Trojan.

  6. Adds the value:

    "Start"="ok"

    to the registry key:

    HKEY_LOCAL_MACHINE\Software\Microsoft\DirectX

  7. Sets itself up as a server and listens for incoming connections on ports 29,999 and 30,303.


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: Heather Shannon

Discovered: May 02, 2003
Updated: February 13, 2007 12:00:46 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. Update the virus definitions.
  2. Do one of the following:
    • Windows 95/98/Me: Restart the computer in Safe mode.
    • Windows NT/2000/XP: End the Trojan process.
  3. Run a full system scan and delete all the files detected as Backdoor.AntiLam.20.K (or similar variants), and PWS.Hooker.Trojan.
  4. Reverse the changes that the Trojan made to the registry.
  5. Reverse the modifications to the System.ini and Win.ini files (Windows 95/98/Me).
For details on each of these steps, read the following instructions.

1. 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.

2. Restarting the computer in Safe mode or ending the Trojan process
    Windows 95/98/Me
    Restart the computer in Safe mode. All the Windows 32-bit operating systems, except for Windows NT, can be restarted in Safe mode. For instructions, read the document, "How to start the computer in Safe Mode."

    Windows NT/2000/XP
    To end the Trojan process:
    1. Press Ctrl+Alt+Delete once.
    2. Click Task Manager.
    3. Click the Processes tab.
    4. Double-click the Image Name column header to alphabetically sort the processes.
    5. Scroll through the list and look for internat.exe.
    6. If you find the file, click it, and then click End Process.
    7. Exit the Task Manager.
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 infected with Backdoor.AntiLam.20.K or PWS.Hooker.Trojan, click Delete.

4. Reversing the changes made to the registry

CAUTION : Symantec strongly recommends that you back up the registry before you make 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, and then click OK. (The Registry Editor opens.)
  3. Navigate to each of the keys:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

  4. In the right pane, delete the value:

    "SVCHOST"="%system%\internat.exe"

  5. Delete the registry key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\KeyConfig

  6. Navigate to the key:

    HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DirectX

  7. In the right pane, delete the value:

    "Start"="ok"

  8. Exit the Registry Editor.

5. Reversing the modifications made to the System.ini and Win.ini 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 backup copies of the System.ini and Win.ini files, which you need to edit. If the backup copies exist, they will be in the C:\Windows\Recent folder. Symantec recommends that you delete these files before continuing with the steps in this section. To do this:
      1. Start Windows Explorer.
      2. Browse to and select the C:\Windows\Recent folder.
      3. In the right pane, select the Win.ini and System.ini files and delete them. Both files will be regenerated when you save your changes to them in the following steps.

  2. Click Start, and then click Run.
  3. Type the following:

    edit c:\windows\system.ini

    and then click OK. (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:

    shell = Explorer.exe C:\WINDOWS\SYSTEM\internat.exe

    (The path may be different.)

  5. If this line exists, delete everything to the right of Explorer.exe.

    When you are done, it should look like:

    shell = Explorer.exe

  6. Click File, and then click Save.

  7. Click File, and then click Exit.

  8. Repeat steps b through g to edit the file:

    c:\windows\win.ini.

    In this case you should delete the line:

    run=C:\WINDOWS\SYSTEM\internat.exe


Writeup By: Heather Shannon