Adding a Watermark Overly on Windows 11 System-Level UI

Question

Hello everyone,

I have been trying to implement a (C# WinFrom) application that adds a watermark over all user’s screens (as a TopMost overly which does not affect user’s interactions) to make it easier to know from where the leak originated (if the user take screenshots); which I partially achieved.

Except there are some places where the user’s could take advantage of and take screenshots, those places mostly are Windows system-level UI; such as:

1. When the user clicks Win+Tab.
2. When the user clicks Alt+Tab.
3. When the user clicks Start menu.
4. When the user hovers over opened applications via Taskbar thumbnail live preview.

What I am looking for coming here is for someone to help and guide me on how to achieve this if all possible. I have tried to sign the application and install it with administrator privileges but it did not work so maybe I am missing something out.

Here are some edited pictures to demonstrate what I want the watermark to be displayed over:

Thanks in advance.

Answer 1

Implementing a system-wide watermark that covers all scenarios, including system-level UI, is challenging due to Windows security measures.

One approach could involve using DirectX or the Desktop Window Manager (DWM) APIs to create a more powerful overlay. This is a complex solution that might allow you to render above certain system-level interfaces. However, this requires a deep understanding of DirectX and low-level Windows API, and it's still limited by Windows security features.