No matter what brand and model of ble chip your mobile phone is equipped with, it contains minor defects, making its signal have a unique fingerprint. The fingerprint is unique to the single chip. According to researchers at the University of California, San Diego, if someone can initially get a fingerprint that they know the ble signal from your phone, they can then determine whether the phone is in a given location. They can do this with a cheap receiver that tells them if the area is sending a signal with the fingerprint.
In the field test, scientists were able to identify multiple unique ble fingerprints from mobile phones in crowded public areas. In addition, they were able to track a volunteer carrying a mobile phone when he entered and left their home. That is to say, the tracking technology has many limitations.
First, the receiver must be within the physical range of the ble signal, usually no more than 30 feet (9 m). In addition, the technology will require a considerable amount of technical expertise from those who track it. Finally, changes in factors such as ambient temperature may change the unique characteristics of the signal. Nevertheless, the UCSD team is now studying how to hide ble fingerprints of mobile phones through digital signal processing in device firmware.