Bluetooth Low Energy (BLE) changed everything. It allowed devices to communicate using tiny amounts of power, enabling the creation of "Find My" trackers like AirTags. But this same technology is what allows us to find them.
The "Advertising Packet"
BLE devices don't just sit there silently. To be "findable", they must broadcast their existence. About every 2 seconds, an AirTag wakes up and shouts a digital message: "Here I am! Here is my ID!"
This message is called an Advertising Packet. It is unencrypted and public. Any Bluetooth antenna nearby can hear it.
RSSI: The Hot/Cold Game
When Stop Stalker picks up this packet, it measures the signal strength, known as RSSI (Received Signal Strength Indicator).
- -30 dBm: The device is practically touching your phone.
- -60 dBm: The device is a few meters away.
- -90 dBm: The device is far away or buried deep inside luggage.
By watching the RSSI number change as you walk around a room, you can triangulate the position of the tracker. If the number goes up (gets closer to zero), you are getting "warmer". If it drops, you are getting "colder".
Digital Fingerprinting
Stop Stalker analyzes the data payload of the packet to identify the manufacturer. Apple AirTags have a specific signature. Tile trackers have another. By matching these signatures, the app can tell you exactly what kind of device is stalking you, not just that something is there.