Registry Tip #56: Disable OS/2 and/or Posix SUBSYSTEMS

Hits: Failed to execute CGI : Win32 Error Code = 3

It is a good security policy to disable optional, unused sub-systems Microsoft included with Windows - NT, W2K, & XP. To disable the obsolete and insecure posix and os/2 subsystems by clearing the multistring value named "Optional" in the Registry entry:

Hive: HKEY_LOCAL_MACHINE
Key: SYSTEM\CurrentControlSet\Control\Session Manager\Subsystems

Under some OSs the string with have both "os/2" and "posix" strings. XP generally just has "posix". In any case, clear the value.





Good place to start.