Oh good grief. It’s NOT microwaves!
It’s a sonic data transmitter that spies use to extract data by sound waves without tripping RF sensors.
In contrast, microwaves are RF. Microwaves are easily detected with RF sensors.
If the attacks were by microwaves, our RF sensors would have detected them.
Soundwaves aren’t RF, though.
A bug inside an embassy that transmits by ultrasound WON’T trip an RF detector.
So if you want to eavesdrop on diplomats inside an embassy, you use a sonic transmitter (bug).
...of course, loud ultrasonic transmissions are hazardous to humans nearby.