Disable OS/2 and/or Posix subsystems

by Wayne Maples [Published on 20 April 2004 / Last Updated on 20 April 2004]

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.

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