Matt Edmondson, a hacker and digital forensics expert, built a Raspberry Pi-powered anti-tracking tool that “scans for nearby devices and alerts you if the same phone is detected multiple times within the past 20 minutes,” reports Wired. The device, which can be carried around or placed in a car, consists of parts that cost around $200 in total. From the report: The homemade system works by scanning for wireless devices around it and then checking its logs to see whether they also were present within the past 20 minutes. It was designed to be used while people are on the move rather than sitting in, say, a coffee shop, where it would pick up too many false readings. The anti-tracking tool, which can sit inside a shoebox-sized case, is made up of a few components. A Raspberry Pi 3 runs its software, a Wi-Fi card looks for nearby devices, a small waterproof case protects it, and a portable charger powers the system. A touchscreen shows the alerts the device produces. Each alert may be a sign that you are being tailed. The device runs Kismet, which is a wireless network detector, and is able to detect smartphones and tablets around it that are looking for Wi-Fi or Bluetooth connections. The phones we use are constantly looking for wireless networks around them, including networks they’ve connected to before as well as new networks.
Edmondson says Kismet makes a record of the first time it sees a device and then the most recent time it was detected. But to make the anti-tracking system work, he had to write code in Python to create lists of what Kismet detects over time. There are lists for devices spotted in the past five to 10 minutes, 10 to 15 minutes, and 15 to 20 minutes. If a device appears twice, an alert flashes up on the screen. The system can show a phone’s MAC address, although this is not much use if it’s been randomized. It can also record the names of Wi-Fi networks that devices around it are looking for — a phone that’s trying to connect to a Wi-Fi network called Langley may give some clues about its owner. “If you have a device on you, I should see it,” he says. In an example, he showed WIRED that a device was looking for a network called SAMSUNGSMART.
To stop the system from detecting your own phone or those of other people traveling with you, it has an “ignore” list. By tapping one of the device’s onscreen buttons, it’s possible to “ignore everything that it has already seen.” Edmondson says that in the future, the device could be modified to send a text alert instead of showing them on the screen. He is also interested in adding the capability to detect tire-pressure monitoring systems that could show recurring nearby vehicles. A GPS unit could also be added so you can see where you were when you were being tracked, he says. […] Edmondson has no plans to make the device into a commercial product, but he says the design could easily be copied and reused by anyone with some technical knowledge. Many of the parts involved are easy to obtain or may be lying around the homes of people in tech communities. For those interested, Edmondson open-sourced its underlying code and plans to present the research project at the Black Hat security conference in Las Vegas this week.