CHAPTER 1
Introduction
Exltration of private data is a threat on mobile devices. Published attacks to
exltrate data from mobile devices use various communication channels such as NFC,
Bluetooth, Wi-Fi and FM radio receivers found in those devices [4, 8]. Availability
of these media on mobile devices also provide opportunities for using them as re-
ceivers for data exlteration from other non-mobile devices such as a computer using
electromagnetic emanations [11]. While these media are commonly found in mobile
devices, relying on such media results in attacks for which distance from the target is
a limiting factor. This limitation, however, is absent when the cellular network itself
is used for exltration. The cellular network can be vulnerable to attacks due to the
fact that in most mobile phones the cellular interface (also known as baseband) is
controlled by the main processor of the mobile device, a feature that leaves cellular
media vulnerable to attack [10, 14]. Some published work explores the possibility of
using a text channel provided by the cellular network as a medium for exltration [5].
While the texting over a cellular network does provide a viable option for removing
any distance limitation, it suers from the limitation that a data plan must be pur-
chased for the mobile device, and text usage appears in the phone bill, which likely
makes such an attack transient, at best.
In this project we have demonstrated that the audio media during a voice call
can become a medium for exltration. There are several potential advantages in using
audio during a voice call for exltration. As discussed above, voice does not have any
distance limitation, and such usage is less likely to be observed on a bill. The main
problem in using the audio media is that the voice calls are visually indicated and
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