Backdoor.Death

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Discovered: August 18, 2001
Updated: February 13, 2007 11:37:39 AM
Also Known As: Backdoor.Death.25, Backdoor.Death.26
Type: Trojan Horse
Systems Affected: Windows



Backdoor.Death is a typical Backdoor Trojan, which gives a remote attacker unobstructed access to your computer.

Antivirus Protection Dates

  • Initial Rapid Release version August 18, 2001
  • Latest Rapid Release version January 22, 2018 revision 022
  • Initial Daily Certified version August 18, 2001 revision 002
  • Latest Daily Certified version January 23, 2018 revision 002
  • Initial Weekly Certified release date August 22, 2001

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

Writeup By: Atli Gudmundsson

Discovered: August 18, 2001
Updated: February 13, 2007 11:37:39 AM
Also Known As: Backdoor.Death.25, Backdoor.Death.26
Type: Trojan Horse
Systems Affected: Windows


The backdoor Trojans in this family typically add keys or values to these registry keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\sockets

They may also add load and run lines to the following system files:

C:\Windows\win.ini
C:\Windows\system.ini

Version 26
Backdoor.Death (v26) does the following:

Registry changes

  • Adds the value

    winfont.exe C:\Windows\FONTS\winfont.exe

    to the registry key

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce
  • Adds the values

    internat.exe internat.exe
    winfont.exe    C:\Windows\FONTS\winfont.exe

    to the registry key

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
  • Adds the value

    winfont.exe C:\Windows\FONTS\winfont.exe

    to the registry key

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce

  • Creates the registry key \sockets under the registry key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion.

    It also creates an entire subkey structure under the \sockets subkey.

System file changes
The Backdoor Trojan modifies the following system files:
  • C:\Windows\Win.ini. It adds the following lines:

    load=C:\Windows\FONTS\winfont.exe
    run=C:\Windows\FONTS\winfont.exe
  • C:\Windows\System.ini. It adds the line:

    load=C:\Windows\FONTS\winfont.exe

Dropped files
This Trojan creates the following files on your system:
  • C:\Windows\FONTS\Winfont.exe
  • C:\Windows\System\Internat.exe (the original is saved as C:\Windows\Interface.dll, Kernel1.exe, Kernel_1.exe, Kernel2.exe, or Kernel_2.exe in the Windows \Temp folder.)
  • C:\Windows\System\Runexec.dll
  • C:\Autorun.inf
  • C:\Windows\Avp32.ini
  • C:\Windows\Avpm.ini

Version 26b
Backdoor.Death (v26.b) behaves in exactly the same manner as v26, except this version uses the value

winsock     C:\WINDOWS\SYSTEM\winsock.exe

instead of the value

winfont.exe      C:\Windows\FONTS\winfont.exe

when it adds the values to these keys:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
KEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce

Version 26c
Backdoor.Death (v26c) Backdoor.Death (v26.b) behave in exactly the same manner as v26, except this version

adds the value

winsys.exe %system%\winsys.exe

to the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run

and it creates the registry key

\Socket

under the registry key

HKEY_LOCAL_MACHINE\Software\Microsoft

This version creates the files %system%\Winsys.exe and %system%\Runexec.dll.

Version 25
Backdoor.Death (v25) does the following:

Registry changes
  • It adds the value

    internat.exe internat.exe

    to the registry key

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
  • It adds the value

    winupdate.exe C:\Windows\FONTS\winupdate.exe

    to the registry key

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce
  • It creates the registry key

    \socket

    under the registry key

    HKEY_LOCAL_MACHINE\Software\Microsoft

    The Backdoor Trojan also creates an entire subkey structure under the \socket subkey.

System file changes
It modifies the following system files:
  • C:\Windows\Win.ini. It adds the following lines:

    load=C:\Windows\FONTS\winupdate.exe
    run=C:\Windows\FONTS\winupdate.exe
  • C:\Windows\System.ini. It adds the line load=C:\Windows\FONTS\winupdate.exe.

Dropped files
This Trojan creates the following files on your system:
  • C:\Windows\FONTS\Winupdate.exe
  • C:\Windows\System\Internat.exe (the original is saved as C:\Windows\Interface.dll, Kernel1.exe, Kernel_1.exe, Kernel2.exe, or Kernel_2.exe in the C:\Windows\Temp folder.)
  • C:\Windows\System\Runexec.dll
  • C:\Autorun.inf
  • C:\Windows\Avp32.ini
  • C:\Windows\Avpm.ini


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: Atli Gudmundsson

Discovered: August 18, 2001
Updated: February 13, 2007 11:37:39 AM
Also Known As: Backdoor.Death.25, Backdoor.Death.26
Type: Trojan Horse
Systems Affected: Windows



NOTE: These instructions are for all current and recent Symantec antivirus products, including the Symantec AntiVirus and Norton AntiVirus product lines

  1. Update the virus definitions.
  2. Run a full system scan and delete all the files detected as Backdoor.Death.
  3. Reverse the changes made to the registry.
  4. (Windows 95/98/Me only). Remove references to the Trojan from the Windows startup files.
For details on how to do this, read the following instructions.

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 the 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) line at the top of this writeup.
  • 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) line at the top of this writeup.

    The Intelligent Updater virus definitions are available here. For detailed instructions on how to download and install the Intelligent Updater virus definitions from the Symantec Security Response Web site, click here.

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.Death, write down the name and location of the infected file, and then click Delete.


Editing the registry

CAUTION : We strongly recommend that you back up the system registry before making any changes. Incorrect changes to the registry could result in permanent data loss or corrupted files. Make sure you modify the specified keys only. Refer to the document How to back up the Windows registry before proceeding.

NOTE: You will not find all the values or keys on all the systems.
  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 and select the key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run.
  4. Refer to the list of infected files you created while following the instructions in the previous section. In the right pane, look at the entries in the Name and Data columns.
  5. If you find an entry that refers to a file that was detected as infected, select the entry, press Delete, and then click Yes to confirm.
  6. Repeat steps 3 to 5 for the following registry keys:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce
  7. Navigate to and select the key HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion.
  8. Under this key, look for the \Sockets subkey. If it exists, delete it.
  9. Navigate to and select the key HKEY_LOCAL_MACHINE\Software\Microsoft.
  10. Under this key, look for the \Socket subkey. If it exists, delete it.
  11. Exit the Registry Editor.
Removing references to the Trojan from the Windows startup files

NOTES:
  • The instructions in this section applies to Windows 95/98/Me only. It is not necessary to do this if you are running Windows NT/2000/XP
  • For Windows Me users only: Due to the file-protection process in Windows Me, there is a backup copy of the file that you are to edit in the C:\Windows\Recent folder. We recommend that you delete this file before you continue with the steps in this section. To do so using Windows Explorer, go to the C:\Windows\Recent folder, and in the right pane delete the Win.ini file. It will be regenerated as a copy of the file that you are to edit when you save your changes to that file.
  1. Click Start, and then click Run.
  2. Type the following, and then click OK.

    edit c:\windows\win.ini

    The MS-DOS Editor opens.

    NOTE: If Windows is installed in a different location, make the appropriate path substitution.

    CAUTION: The steps that follow instruct you to remove text from the load= and run= lines of the Win.ini file. If you are using older programs, they may be loading at the time of startup from one of these lines. Make sure that you remove only the lines shown.
  3. Locate the load= and run= lines within the [windows] section of the Win.ini file; this section is usually located near the top of the file.
  4. Check to see whether these lines look like the following:

    load=C:\Windows\FONTS\winfont.exe
    run=C:\Windows\FONTS\winfont.exe
  5. If they do, for each line do the following:
    1. Position the cursor immediately to the right of the equal (=) sign.
    2. Press Shift+End to select all the text to the right of the equal sign, and then press Delete.
  6. Click File, click Exit, and then click Yes when you are prompted to save the changes.
  7. Click Start, and then click Run.
  8. Type the following, and then click OK.

    edit c:\windows\system.ini

    The MS-DOS Editor opens.

    NOTE: If Windows is installed in a different location, make the appropriate substitution.
  9. Locate the line

    load=C:\Windows\FONTS\winfont.exe

    within the [boot] section of the System.ini file; the section is usually located near the top of the file.
  10. Select, and then delete this line.
  11. Click File, click Exit, and then click Yes when you are prompted to save the changes.


Writeup By: Atli Gudmundsson