Preventing malicious users from tampering with the Windows operating system on your kiosk necessitates that system keystrokes like Ctrl-Alt-Del be blocked. This can be surprisingly difficult since Windows doesn’t give you a built in method for doing this. The next logical step would be to have your kiosk application filter out these keystrokes which turns out to be a problem since your kiosk application is running in user move not kernel mode (see user mode vs. kernel mode explanation).
This leaves you with three options:
- Create a kernel mode upper filter driver that listens for system keystrokes and discards them before they reach the operating system.
- Use a 3rd party kiosk lockdown software that filters keystrokes for you.
- Replace the physical keyboard with a touchscreen keyboard that does not include any modifier keys (i.e. Ctrl, Alt, Shift, Windows Key, etc…)
Option 1 – Creating a keyboard filter driver to filter keystrokes
Creating a keyboard filter driver is not for the faint of heart. It will require that you dust off all those seemingly useless C++ skills you learned back in college. Microsoft provides a good C++ code example for creating a keyboard filter driver which should be used as your starting point.
Option 2 – Using a 3rd party kiosk lockdown software to filter keystrokes
KioskSimple makes it easy to filter out system keystrokes like Ctrl-Alt-Del on your kiosk. We pre-define all of the well-known system keystrokes so you don’t have to scour the internet for every possible keystroke combination. We also make it easy to define your own custom keystroke combinations to filter. This can be useful if your kiosk’s PC has special keystrokes specific to the hardware installed (i.e. the Intel Video Drivers Control Panel)
Option 3 – Replace the physical keyboard with a touchscreen keyboard that does not include any modifier keys (i.e. Ctrl, Alt, Shift, Windows Key, etc…)
As long as the touchscreen keyboard does not include the modifier keys then the user should not be able to enter any system keystrokes into your kiosk like Ctrl-Alt-Del. This also assumes that the USB and PS/2 ports on your kiosk are blocked to prevent a malicious user from connecting a physical keyboard. Your next question will probably be “where can I find a touchscreen keyboard without any modifier keys which will work on my kiosk?” You can either create your own or use the touchscreen keyboard included in KioskSimple.
Conclusion
Filtering system keystrokes like Ctrl-Alt-Del on you kiosk can seem like a real headache. This was one of the more challenging aspects of developing KioskSimple and if you want to save yourself the headache of developing a keyboard filter driver for your kiosk application then please consider our kiosk lockdown software. We offer a free unlimited time demo of KioskSimple for you to try today.
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