In a recent patent filed by Apple in 2017, the company describes how it intends to prevent iPhones dialing into fake cell phones and being able to be tapped.
Patent Application 20190068651, published by the US Patent and Trademark Office at the end of February 2019, is called the “Cellular Security Framework” and describes how a smartphone, when connecting to a base station of a cellular network, checks more closely whether the information being exchanged is signal strength and network identifier of the base station to the location of the smartphone and the network operator or doubts exist on the authenticity of the base station, which in turn lead to a termination of communication with the affected mobile radio cell, adding the affected, supposedly fake base station to a blacklist, or at least in could result in a safety alert to the user.
Better protect IMSI
The background to this additional security measure is that the smartphone, if possible, no longer transmits the user's “International Mobile Subscriber Identity” (IMSI) to a fake base station. Fake cell phones, so-called IMSI catchers, are used repeatedly to intercept and use this information from nearby smartphones. The IMSI is used to uniquely identify the network participants. After the announcement of this identifier, security gaps in mobile radio protocols can be used to decrypt the encrypted IMSI in LTE and 5G networks by means of IMSI cracking and to listen to messages and telephone calls. In addition, it is possible to track the location of the user or the smartphone.
Gaps and espionage are reality
Corresponding security vulnerabilities have also recently been demonstrated in the supposedly better-protected 5G mobile communications standard and require extensive adjustments by both the GSMA and network operators. In 2017, a nationwide deployment of downtown IMSI catchers around government buildings was revealed in the Canadian capital of Ottawa.
Also prosecution affected
If Apple introduces protection in a future operating system version of iOS, it would also hamper the work of law enforcement agencies using IMSI catchers to locate smartphones. However, the technology mentioned in the patent is still not used in iOS.