The QuadRF (pictured above) a phased-array radio built around a Raspberry Pi 5 and an FPGA board with picosecond-level timing. It does advanced signal processing and beamforming. It can see WiFi through walls and track drones in flight. If the open source community can come up with something like this, just imagine what governments are capable of. When you plug a computer into a network, tools like Wireshark can show all the hidden traffic you might not even know is there. WiFi packets are the same, but those travel through the air, allowing snooping without physical access.