Isolation is a prime ingredient of information security. The air-gap is the best way to isolate systems. Only wireless communication can transport data across these gaps. Apart from Wi-Fi the signals of mobile radio communication are very common. At DeepSec we have seen a lot of hacking when it comes to mobile phones and their networks. Mordechai Guri and Yisroel Mirsky (both of Ben-Gurion University of the Negev) held a talk about how to overcome the air-gap barrier by means of cellular frequencies.
Their presentation addresses the way of exfiltrating data across the air-gap: „Although the feasibility of invading such systems has been demonstrated in recent years, exfiltration of data from air-gapped networks is still a challenging task. In this talk we present GSMem, a malware that can exfiltrate data through an air-gap over cellular frequencies. Rogue software on an infected target computer modulates and transmits electromagnetic signals at cellular frequencies by invoking specific memory-related instructions and utilizing the multichannel memory architecture to amplify the transmission. Furthermore, we show that the transmitted signals can be received and demodulated by a rootkit placed in the baseband firmware of a nearby cellular phone. We present crucial design issues such as signal generation and reception, data modulation, and transmission detection. We implement a prototype of GSMem consisting of a transmitter and a receiver and evaluate its performance and limitations. Our current results demonstrate its efficacy and feasibility, achieving an effective transmission distance of 1-5.5 meters with a standard mobile phone. When using a dedicated, yet affordable hardware receiver, the effective distance reached over 30 meters.“
Wireless communication is all over the place and extremely common. It’s time to re-evaluate what air-gap really means.