The hacker told how to crack the electronic bracelet home arrest

Fragment of the poster of the movie "Escape plan"



Computer security enthusiast William Turner, known in special circles as Amm0nRa, managed to “trick” the electronic bracelet used in the United States to track convicts under house arrest. He managed to successfully bypass all the degrees of protection of the bracelet, which is usually worn on the ankle, including fake GPS-coordinates and GSM-alerts. Turner shared his discoveries with his colleagues at the hacker conference DEF CON .



“It’s generally accepted that these systems are safe only because they are part of the justice system,” Turner explains as part of his presentation, “but they are far from perfect.”

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According to Turner, who dealt with one specific device made in Taiwan, for other similar devices, similar workarounds will also work. In this report, he spoke about the device manufactured by GWG International. It uses GPS and cell-based orientation to determine a person’s location, and sends these coordinates via cellular to the appropriate institution.





William Turner demonstrates the device after his talk at DEF CON.



A theoretical attacker who needs to be technically savvy will need a self-made Faraday cage, a software-defined radio system ( Software-defined radio, SDR ), and a smartphone.



Turner describes the hacking process as follows. Placing the bracelet in a cell, it can be disassembled, and remove the SIM card. The alarming message about removing the bracelet will need to be intercepted by creating a false cell tower using the SDR - then the bracelet will think that the message was successfully delivered. After that, you can insert the SIM card into the phone, determine the phone number to which it is registered, and, replacing the sender, send a false SMS to the supervisory authorities from this number with the wrong coordinates.



Turner spoke at the conference about his concerns about the relative ease of breaking the bracelet. Even if we accept the fact that few of the convicts have the necessary technical knowledge, there is always the possibility that someone will create a device to automatically carry out all of these operations and will sell it on the black market.



In this case, the hacker said that in this case, he did not even try to contact the manufacturer to report vulnerabilities. He has been studying the security of similar devices for some time, but all his previous attempts to communicate with their manufacturers ended in nothing. Manufacturers did not respond to his messages, and, apparently, were not interested in improving their products.



Electronic bracelet was invented by scientists at Harvard University in the 1950s, and was first tested on a criminal in 1983. By 2007, more than 130,000 cases of its use in the United States are known, and it has gained relative popularity in the UK, but is not particularly common in other European countries. In Russia, the decision to use such bracelets was made in 2010. Currently, the Russian version of SEMPL bracelets is operated in 80 regions of the Russian Federation.