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Keyboard Filter Overview (POSReady 7)

4/29/2013

Keyboard Filter provides a predefined list of keys and key combinations that you can block on your device. For example, you might want to block the keyboard shortcut Ctrl+Alt+Del, which enables or disables secure logon; or you might want to prevent users from locking a computer terminal by using Windows+L. Using Group Policy, you will specify policies that configure the keyboard filter so that key sequences or hot keys are blocked. In addition, you may have unique requirements for keys that you want to block on your device. Keyboard Filter enables you to create your own custom key filters.

Keyboard Filter is configured by using the Local Group Policy Editor (Gpedit.msc).

Hh273232.note(en-US,WinEmbedded.21).gifNote:
This file is located at C:\Windows\System32\Gpedit.msc.

The Local Group Policy Editor is a Microsoft Management Console (MMC) snap-in that provides a single user interface through which all the Computer Configuration and User Configuration settings can be managed for your device. Administrators can configure policy settings that are applied regardless of who logs on to the device.

Hh273232.note(en-US,WinEmbedded.21).gifImportant:
You must be logged on with administrative credentials to open the Local Group Policy Editor.

You can also use your predefined and custom key filter settings on other devices by using Group Policy.

Keyboard Filter includes many frequently used predefined key filters. You can use these to quickly enable key filtering on your device.

The predefined key filters are grouped into the following categories:

  • Accessibility keys
  • Application keys
  • Desktop and shell keys
  • Modifier keys
  • Security keys
  • Windows management keys

For more information about how to configure predefined key filters, see Predefined Key Filter Configuration.

For the list of predefined key filters that are included in Keyboard Filter, see Predefined Key Filter Reference.

Virtual keys are used to map keys or key combinations to create your own custom key filters in Keyboard Filter. Virtual keys are grouped into the following supported categories:

  • Modifier keys, such as the Alt, Ctrl, Shift, and Windows keys.
    Hh273232.note(en-US,WinEmbedded.21).gifNote:
    Modifier keys are not supported as a standalone or final key in a custom key filter; instead, use a predefined key filter to block modifier keys.
    Hh273232.note(en-US,WinEmbedded.21).gifNote:
    For certain keys, for example, PrintScrn, ScrollLock, and Break, one-sided modifier keys will not work. Use the generic modifier instead; for example, use Alt instead of RAlt.
  • System keys, such as the Backspace, Clear, and Tab keys.
  • Cursor keys, such as the End, Home, and Insert keys.
  • Less common system keys, such as the Select and Execute keys.
  • Function keys, such as the numbered keys F1 through F12 or higher.
  • State keys, such as the CapsLock and ScrollLock keys.
  • OEM keys, such as the Register and Unregister keys; and the Oem-numbered keys, for example, Oem1.
  • ICO keys

The following keys may exist on certain keyboards but are not supported in the current release (some keys might be supported by a different driver):

  • Browser keys, such as Back and Forward keys.
  • Media keys, such as the Mute key.
  • ICO keys
  • Additional keys, such as Play and Zoom keys.
  • International keys, such as Kana and Kanji keys.

For more information about how to create custom key filters, see Custom Key Filter Configuration.

For the list of virtual keys that are defined for use in Keyboard Filter, see Virtual Key Reference.

Keyboard Filter includes event logging to help satisfy debugging and auditing requirements. Event logging is also used by administrators to determine how Keyboard Filter is operating.

Keyboard Filter provides the following event log information:

  • Service errors
  • Service status
  • Service filter state changes

For more information about event logging in Keyboard Filter, see Event Log Reference.

There are several items that you should consider as you implement predefined key filters or create your own custom key filters:

  • Some non-Microsoft keyboard drivers may bypass the Keyboard Filter driver.
  • Some custom hardware may bypass the Keyboard Filter driver.
  • Some POS keyboards may have custom keys that generate scan code sequences that are not filterable. For example, a POS keyboard may have a double zero key (00), used for amounts like $1.00, that may not be filterable.
  • Keyboard Filter will filter keys from all the keyboards that are attached to a device.
  • On some portable computers or on devices that have compact keyboards, the function key (Fn) may enable multimedia keys (for example, the arrow keys).
  • Some virtual keys may not be supported.
    For more information about virtual key support in Keyboard Filter, see Virtual Key Reference.
  • Key filters are not supported for On-Screen Keyboard (OSK).
    For more information, see Keyboard Filter and On-Screen Keyboard.
  • Keyboard Filter supports up to 1000 custom key filters.
  • The Keyboard Filter service may have to be restarted after a keyboard layout change.
    For more information about how to restart the service, see Keyboard Filter Service.
  • Custom key filters must be defined by using the English names for virtual keys.
    For information about how to use Keyboard Filter with non-US keyboards or non-English languages, see Using Keyboard Filter with Non-English Interfaces.

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