A known security hole in the networking protocol used by cellphone providers around the world played a key role in a recent string of attacks that drained bank customer accounts, according to a report published Wednesday.
The unidentified attackers exploited weaknesses in Signalling System No. 7, a telephony signaling language that more than 800 telecommunications companies around the world use to ensure their networks interoperate. SS7, as the protocol is known, makes it possible for a person in one country to send text messages to someone in another country. It also allows phone calls to go uninterrupted when the caller is traveling on a train.
The same functionality can be used to eavesdrop on conversations, track geographic whereabouts, or intercept text messages. Security researchers demonstrated this dark side of SS7 last year when they stalked US Representative Ted Lieu using nothing more than his 10-digit cell phone number and access to an SS7 network.