Backdoor.Roxrat.12

Symantec Security Response - Backdoor.Roxrat.12

Backdoor.Roxrat.12 is a variant of Backdoor.Roxrat. It gives an attacker unauthorized access to an infected computer. The Trojan attempts to disable some major antivirus and firewall products by terminating the active processes that are in a list that the Trojan maintains.

It opens TCP ports 10666, 65000, and 65010 to connect to the hacker.

This threat is written in the Borland Delphi programming language.

Type: Trojan Horse
Infection Length: 716,800 bytes
Systems Affected: Windows 95, Windows 98, Windows NT, Windows 2000, Windows XP, Windows Me
Systems Not Affected: Macintosh, OS/2, Unix, Linux


technical details

When Backdoor.Roxrat.12 runs, it does the following:

It copies itself as,

• C:\%windir%\Shell64.exe
• C:\%system%\Zbios.exe

NOTES:

• %windir% is a variable. The Trojan locates the Windows installation folder (by default this is C:\Windows or C:\Winnt) and copies itself to that location.
• %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/Millenium), C:\Winnt\System32 (Windows NT/2000), or C:\Windows\System32 (Windows XP).

It adds the value

Microsoft Shell 64 C:\%windir%\Shell64.exe

to the registry keys

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices

so that the Trojan runs each time that you start Windows.

It also modifies the registry key

HKEY_LOCAL_MACHINE\Software\CLASSES\txtfile\shell\open
ommand

so that the (Default) value is

C:\%System%\Zbios.exe /NOTEPAD "%1""

As a result of this modification, Zbios.exe runs each time that you open a text file, and the text file opens in Notepad.

In addition to the registry modification, the Trojan modifies the following startup files (on Windows 95/98/Millenium-based computers only) so that it runs when you restart Windows:

• Win.ini
  
  [Windows]
  run=C:\%Windir%\Shell64.exe
  
• System.ini
  
  [boot]
  shell=Explorer.exe C:\%Windir%\Shell64.exe

The Trojan attempts to disable some major antivirus and firewall products by terminating the active processes that are in a list that the Trojan maintains.

It opens TCP ports 10666, 65000, and 65010 to connect to the hacker.

removal instructions

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. Do one of the following:
  • 
    Windows 95/98/Millenium: Restart the computer in Safe mode.
    Windows NT/2000/XP: Stop the Trojan process.
  3. Run a full system scan, and delete all files that are detected as Backdoor.Roxrat.12.
  4. Remove the values that the Trojan added to the registry.
  5. Remove the lines that Trojan added to Win.ini and System.ini.

To reverse the changes that the Trojan 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 only the keys that are specified. Read the document How to make a backup of the Windows registry for instructions.

• 
  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 the key
  
  HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
  
  4. In the right pane, delete the value
  
  Microsoft Shell 64 C:\%Windir%\Shell64.exe
  
  5. Navigate to the key
  
  HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunServices
  
  6. In the right pane, delete the value
  
  Microsoft Shell 64 C:\%Windir%\Shell64.exe
  
  7. Navigate to the key
  
  HKEY_LOCAL_MACHINE\Software\CLASSES\txtfile\shell\open
  ommand
  
  8. In the right pane, double-click (Default).
  9. Delete the contents of the Value Data box, and replace it with the correct path, file name, and parameters. These will vary, depending on the operating system. To determine this, you may need to look at that same key on a properly functioning computer that has the same operating system and configuration. Two common values are:
  
  Windows 98: C:\%Windir%\Notepad.exe %
  Windows 2000: C:\%System%\NOTEPAD.EXE %1
  
  10. Exit the Registry Editor.

To remove the text that the Trojan added to the Win.ini and System.ini files:

NOTE for Windows Me users only: Due to the file-protection process in Windows Me, a backup copy of the file that you are about to edit exists in the C:\Windows\Recent folder. Symantec recommends that you delete this file before you continue with the steps in this section. To do this using Windows Explorer, go to C:\Windows\Recent, and in the right pane select the Win.ini file and delete it. 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.
  
  3. In the [windows] section of the file, look for an entry similar to the following:
  
  run=C:\%Windir%\Shell64.exe
  
  4. Select the entire line. Be sure that you have not selected any other text, and then press Delete.
  5. Click File, and click Save.
  6. Click File, and click Exit.
  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 path substitution.
  
  9. In the [boot] section, look for the line
  
  shell=explorer.exe C:\%Windir%\Shell64.exe
  
  10. Delete the text
  
  C:\%Windir%\Shell64.exe
  
  so that the line contains only the text
  
  shell=explorer.exe
  
  11. Click File, and click Save.
  12. Click File, and click Exit.