If you have a phone that isn’t a CryptoPhone 500 and live in the U.S., you’re likely to have your phone “attacked” by an “IMSI catcher” up to 80-90 times per hour, according to ESD America, the company promoting the CryptoPhone 500 in the U.S. The CryptoPhone is a security-"hardened" Galaxy S3 device, and the company has removed 468 vulnerabilities removed from the stock operating system.
An IMSI catcher is a device that acts as a fake cell tower and forces your phone to connect to it when in range, gaining access to much of your communications (including SMS, voice and video-calls) because of vulnerabilities in the baseband software of the device and poor encryption algorithms.
The 2G network is by far the most vulnerable, using three-decades-old encryption algorithms that can be decrypted on the fly, but the new IMSI catchers being sold by private companies to authorities in the U.S. also promise to acquire access to 3G, and even the more recent 4G networks, which are supposed to have much better security.
GSMK, the German company making an ultra-secure Android-based smartphone meant to foil surveillance by governments or anyone else, says it detected 17 such fake cell towers in the U.S. on a casual drive through the country.
Most of the attacks from these fake cell towers happen against the baseband processor of the phones. The software for these baseband processors is usually just a proprietary black box that doesn’t allow anyone to see what’s happening inside other than the company making the baseband processor or hackers who have found vulnerabilities in it.
GSMK has developed a baseband firewall technology for the CryptoPhone’s baseband processor that allows the phone to catch all attacks from fake cell towers and block them. While the CryptoPhone 500 was able to block these attacks, an iPhone and a Galaxy S4 couldn’t, and in fact didn’t even know the attacks were happening in the first place:
”As we drove by, the iPhone showed no difference whatsoever. The Samsung Galaxy S4, the call went from 4G to 3G and back to 4G. The CryptoPhone lit up like a Christmas tree,” ESD America CEO Les Goldsmith told PopSci.
A phone like CryptoPhone doesn’t come cheap, though. GSMK sells each unit for $3,500, which obviously most people can't afford. The next best thing these days in terms of a secure phone is the Blackphone. However, so far the Blackphone doesn’t provide anything that protects against baseband attacks. If the attackers can get inside the phone through the baseband OS, then it won’t matter much if the communication is encrypted.
Phones like CryptoPhone 500 or Blackphone usually end up being used by companies or government officials rather than regular individuals, so to make sure most people’s communications are protected by default (rather than vulnerable by default), we need companies like Google, Apple and Microsoft to stand behind their users and add similar protections to all the phones using their platforms.