Mystify.scr

Windows screensaver Reference

A .scr file is a screensaver on Windows. The file is a normal executable in the PE format with a different extension. Windows starts it after a period without user input. The program draws animations or blanks the screen, and it ends on input. Attackers also use the extension to hide executables, thus care with unknown .scr files is necessary.

A file extension is only a part of the file name. It does not give a guarantee about the format or the content of a file. But on Windows, the extension selects the program that opens the file.