A rogue base station attracts mobiles by offering a stronger signal, and once connected forces the mobile back to 2G technology, where encryption is negligible and easily bypassed. This attack was demonstrated recently at the Ruxcon Security Conference, in Melbourne.
Andy Lilly, director and co-founder of Armour Communications commented; Given the many years of experience and the huge investment in time to develop the specification for the 4G network, it has been assumed that it would be much better at protecting privacy. While it is to some degree, 4G does not solve the issue of potential IMSI catcher style attacks leaving commercial and public sector/government organisations vulnerable.
4G enforces mutual authentication between handset and network base station, unlike 2G/GSM, but it still requires the mobile to transmit its International Mobile Subscriber Identity (IMSI) at least once in order to connect. Also, because 4G coverage is not ubiquitous, a fraudulent base station can trick handsets into downgrading to 2G, meaning any communication, voice, text or attachment can be compromised.
Andy Lilly added; There is currently a proliferation of free apps and services that claim to be secure and encrypted, however, organisations should be careful about using such services. These services are not explicit about exactly what is encrypted and therefore there can be gaps that the user is unaware of. Furthermore, companies should not rely on services over which they have no control for example the carrier service in some countries in order to protect commercially sensitive information on which the success of their business depends.