A hacked feature phone can prevent incoming calls and text messages (SMS) from reaching nearby phones, researchers in Berlin have found. Their study shows that with a few simple hacks to Motorola feature phones, anything operating nearby on a 2G network is susceptible.
In the U.S., AT&T and T-Mobile both utilize a 2G network for voice calls and texts. The second-generation GSM network is the most common cellular network on the planet, with more than 4 billion people worldwide relying on it for calls and texts. The hack changes a phone’s firmware to trick the network out of delivering incoming calls or texts to intended recipients.
The hack could potentially be used to block service to all of the subscribers in a specific service area with a single phone, Technology Review reports. Dr. Jean-Pierre Seifer and his colleagues from the Technical University of Berlin presented their research at the Usenix Security Symposium in Washington last week. A video showcasing the hack is embedded below.
When an SMS or call is sent over a 2G network, cell towers page nearby phones to find the intended recipient. Phones with normal firmware will respond accordingly – only responding to calls and messages meant for their subscriber. But phones hacked by the researchers respond faster, receiving communications intended for another device.
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The researchers say the hack can affect entire location areas, which average 200 square kilometers in Berlin. The team used open-source baseband code to rewrite the firmware for Motorola’s C1 series of phones. They say that 11 hacked phones would be able to take down service completely in a location area for E-Plus, Germany’s third-largest wireless provider.