”Like correctly reporting net frequency in the range 49-51 Hz but reporting false values when outside of that range.” You can’t fake the system frequency like

”Like correctly reporting net frequency in the range 49-51 Hz but reporting false values when outside of that range.” You can’t fake the system frequency like that. Anyone connected to the grid can observe/measure the system frequency trivially - you could do so right now at the nearest 10A socket. The attack you describe would require compromising large numbers of diverse, distributed generation and frequency response assets. It would be like trying to fool everyone into thinking it’s a hot day by hacking every single thermometer!