It is possible to track individuals using Bluetooth signals. So say researchers from the University of California San Diego. They discovered that the Bluetooth signals that mobile phones continuously transmit have a unique fingerprint. This can be used to track individuals. This has never been demonstrated before.
Unique fingerprints unintended result
All mobile devices, including phones, smartwatches and fitness trackers, continuously transmit Bluetooth signals. These signals ensure, among other things, that you can find your phone in Apple’s ‘Find My’ network. For example, corona apps and wireless headphones also use Bluetooth signals.
However, all wireless devices have minor hardware manufacturing flaws that are unique to each device. The researchers call this an “accidental by-product of the production process”. These imperfections in Bluetooth hardware create unique distortions in the signals a device transmits. Institutions and malicious parties can use these disruptions as a fingerprint to track a specific device. It also allows attackers to bypass anti-tracking techniques that manufacturers add to their products.
Previous research has shown that Wi-Fi and other wireless technologies leave wireless fingerprints. It now appears that this form of tracking with Bluetooth is possible; in a very precise way.
“This is important because Bluetooth poses a greater threat in today’s world as it is a frequent and constant wireless signal broadcast by all of our personal mobile devices,” said Nishant Bhaskar, one of the lead authors of the study.
Tracking individuals with bluetooth is complicated
According to the research team, tracking individual devices via Bluetooth is not easy. Previous WiFi fingerprinting techniques are based on the fact that WiFi signals contain a preamble. This is a long, well-known sequence of signals. However, preambles for Bluetooth beacons are very short, which makes for an inaccurate fingerprint. Previous techniques, therefore, do not work when tracking Bluetooth signals.
The researchers designed a method that does not depend on the preamble but looks at the entire Bluetooth signal. Using a self-developed algorithm, they found two different Bluetooth signals that vary based on the defects in the Bluetooth hardware. This allowed the researchers to get the device’s unique fingerprint. They then tested this with real-world experiments. Finally managed to perform a real ‘tracking attack’ by using a fingerprint and following a volunteer as he/, she walked in and out of his/her house.
However, the researchers note that various circumstances will make it difficult for attackers to track people. For example, changes in the ambient temperature can alter the Bluetooth fingerprint. Also, some devices transmit signals of different powers.
This affects the distance at which you could track these devices. In addition, the researchers state that an attacker needs a high degree of expertise to follow the same method as the researchers. Nevertheless, Bluetooth tracking is possible for a large number of devices, and with simple and relatively cheap equipment.
Researchers are working on a solution
The research team is currently working on a way to hide Bluetooth fingerprints. The researchers are trying to find a solution in which the firmware processes the Bluetooth signal in a way that tracking is no longer possible.
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