A very special exe I use for teaching Windows Internals. It's a version 2, somewhat improved, but I have never published v1 though.
It IS NOT harmful, you can use it on prod, but some AV/EDR may warn you it uses some suspicious techniques. It's true, as I try indeed to make it not too obvious. Matter of balance between looking good and being funny ;)
The tool IS NOT persistent. Reboot clears everything, leaving two or three innocent files on your C: volume.
NO ADMIN required. I want to play with you, and not destroy your computer...
The file is (obviously!) digitally signed.
The exe creates "secret.txt" on your desktop, and the challenge is to read its content. Sounds simple, but it depends actually on your skills and knowledge. Try it: run the exe, read the file, enjoy!
I will publish the source code (400LoC of C) in a couple of days. Publishing it right now would spoil the fun :P
Enjoy the C source code :)