Quote:
Backdoor.Death
Discovered on: August 18, 2001
Last Updated on: April 15, 2002 at 04:47:26 PM PDT
Backdoor.Death is a typical Backdoor Trojan, which gives a remote attacker unobstructed access to your computer.
Also Known As: Backdoor.Death.25, Backdoor.Death.26
Type: Trojan Horse
Infection Length: multiple files
Wild:
Number of infections: 0 - 49
Number of sites: 0 - 2
Geographical distribution: Low
Threat containment: Easy
Removal: Easy
Threat Metrics
Wild:
Low
Damage:
Medium
Distribution:
Low
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
It adds the value
winfont.exe C:\Windows\FONTS\winfont.exe
to the registry key
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce
It adds the value
internat.exe internat.exe
to the registry key
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
It adds the value
winfont.exe C:\Windows\FONTS\winfont.exe
to the registry key
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce
It 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
It 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 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
It 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
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, a telnet server, 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.
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.
To remove this Trojan, delete files detected as Backdoor.Death and reverse the changes that it made to the registry and to system files.
To remove the Trojan files:
1. Run LiveUpdate to make sure that you have the most recent virus definitions.
2. Start Norton AntiVirus (NAV), and make sure that NAV is configured to scan all files. For instructions on how to do this, read the document How to configure Norton AntiVirus to scan all files.
3. Run a full system scan.
4. If NAV detects any files as Backdoor.Death, first write down the name and location of the infected file, and then choose to delete it. (You will need this information in the sections that follow.)
NOTE: As an alternative to writing down the file names, you can print a copy of the Norton AntiVirus Activity log. The log contains information on what was detected, the location of the file, and what was done to it. To do this:
1. With NAV still open, click Reports.
2. Double-click "View the log of Norton AntiVirus activities."
3. Click Print.
To edit 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. Please make sure you modify only the keys specified. Please see the document How to back up the Windows registry before proceeding.
1. Click Start, and click Run. The Run dialog box appears.
2. Type regedit and then click OK. The Registry Editor opens.
3. Navigate to and select the following key:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
4. Refer to the list of infected files that 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 following key:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Sockets
8. Select the \Sockets subkey and delete it.
9. Exit the Registry Editor.
Edit Windows startup files
NOTES:
The instructions in this section applies only to Windows 95/98/Me. It is not necessary to do this if you are running Windows NT/2000.
(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 about 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 about to edit when you save your changes to that file.
1. Click Start, and 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 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. See if 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:
a. Position the cursor immediately to the right of the equal (=) sign.
b. Press Shift+End to select all of 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 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.
This completes the removal part of the process. Even though you did so previously, start NAV and run another full system scan. Delete any files that were found to be infected with Backdoor.Death. When you have finished, restart the computer.
