Can a Program Differentiate between User Key Input and Program key Input?

Question

Is it possible for a program to block key input from other programs but NOT key input directly from the user's hand hitting a key on the keyboard?

For example:

ProgramA contains a text field .

ProgramB is Windows On-Screen keyboard.

After selecting the text field in ProgramA, I attempt to press the letter 'c' on the On-Screen Keyboard program but it does not appear in the text field.

However, when I press the letter 'c' directly from my keyboard it appears within the text field of ProgramA.

I know how key events work, how they are queued, and I've seen the BlockInput Function in c++

http://msdn.microsoft.com/en-us/library/windows/desktop/ms646290%28v=vs.85%29.aspx

But that function simply blocks all input.

Ive encountered programs that filter the input in this way and can't seem to figure out how. Am I missing something completely obvious?

This question is mainly pertaining to c++ on the Windows 7 operating system.

Answer 1

You can never be sure if input is coming from hardware. The simplest example is a custom driver wich will simulate real keyboard driven by software input.

Some fancy idea can be attaching microphone to device, to listen for sounds/vibrations for input filtering, but do you mean complete hardware solution or application, wich will be given to personal users?