Sophisticated hackers have long exploited flaws in SS7, a protocol used by telecom companies to coordinate how they route texts and calls around the world. Those who exploit SS7 can potentially track phones across the other side of the planet, and intercept text messages and phone calls without hacking the phone itself.
This activity was typically only within reach of intelligence agencies or surveillance contractors, but now Motherboard has confirmed that this capability is much more widely available in the hands of financially-driven cybercriminal groups, who are using it to empty bank accounts. So-called SS7 attacks against banks are, although still relatively rare, much more prevalent than previously reported. Motherboard has identified a specific bank—the UK’s Metro Bank—that fell victim to such an attack.
The news highlights the gaping holes in the world’s telecommunications infrastructure that the telco industry has known about for years despite ongoing attacks from criminals. The National Cyber Security Centre (NCSC), the defensive arm of the UK’s signals intelligence agency GCHQ, confirmed that SS7 is being used to intercept codes used for banking.
“We are aware of a known telecommunications vulnerability being exploited to target bank accounts by intercepting SMS text messages used as 2-Factor Authentication (2FA),” The NCSC told Motherboard in a statement.