Phone Firewall Identifies Rogue Cell Towers Trying to Intercept Your Calls

Rogue cell phone towers can track your phone and intercept your calls, and it’s only a matter of time before they’re as ubiquitous as GPS trackers. But at least now there’s a way to spot them.

A firewall developed by the German firm GSMK for its secure CryptoPhone lets people know when a rogue cell tower is connecting to their phone. It’s the first system available that can do this, though it’s currently only available for enterprise customers using Android phones.

GSMK’s CryptoPhone 500, a high-end phone that costs more than $3,000 and combines a Samsung Galaxy S3 handset with the CryptoPhone operating system, offers strong end-to-end encryption along with a specially hardened Android operating system that offers more security than other Android phones and the patented baseband firewall that can alert customers when a rogue tower has connected to their phone or turned off the mobile network’s standard encryption.

The problem with rogue cell towers is widespread. The FCC is assembling a task force to address the illicit use of so-called IMSI catchers—the devices that pose as rogue cell towers. But the task force will only examine the use of the devices by hackers and criminals—and possibly foreign intelligence agencies—not their warrantless use by law enforcement agencies bent on deceiving judges about their deployment of the powerful surveillance technology.

IMSI catchers, stingrays or GSM interceptors as they’re also called, force a phone to connect to them by emitting a stronger signal than the legitimate towers around them. Once connected, pings from the phone can help the rogue tower identify a phone in the vicinity and track the phone’s location and movement while passing the phone signals on to a legitimate tower so the user still receives service. Some of the IMSI software and devices also intercept and decrypt calls and can be used to push malware to vulnerable phones, and they can also be used to locate air cards used with computers. The systems are designed to be portable so they can be operated from a van or on foot to track a phone as it moves. But some can be stationary and operate from, say, a military base or an embassy. The reach of a rogue tower can be up to a mile away, forcing thousands of phones in a region to connect to it without anyone knowing.

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