How can I prevent taking screenshots of certain applications?

Question

Windows

There is a program similar to a keylogger that takes screenshots of the screen after a certain period of time. How can I make these screenshots show a black square instead of a specific application?

Answer 1

No way.
Because the program has no idea what the OS will do with those pixels that are drawn - show it on the display or pass it to the logger.

Answer 2

https://en.wikipedia.org/wiki/Video_overlay
This will work in some cases (screenshots will have a black window, etc.). Depends on how you take screenshots.

Answer 3

It strongly depends on what kind of program, and where exactly it takes the data from.
In general-

so that these screenshots show a black square instead of a specific application

Edit a specific application so that it displays a window as a black square.