  Recent research has shown that the integrity of sensor measurements can be
violated through out-of-band signal injection attacks. These attacks target the
conversion process from a physical quantity to an analog property---a process
that fundamentally cannot be authenticated. Out-of-band signal injection
attacks thus pose previously-unexplored security risks by exploiting hardware
imperfections in the sensors themselves, or in their interfaces to
microcontrollers. In response to the growing-yet-disjointed literature in the
subject, this article presents the first survey of out-of-band signal injection
attacks. It focuses on unifying their terminology and identifying commonalities
in their causes and effects through a chronological, evolutionary, and thematic
taxonomy of attacks. By highlighting cross-influences between different types
of out-of-band signal injections, this paper underscores the need for a common
language irrespective of the attack method. By placing attack and defense
mechanisms in the wider context of their dual counterparts of side-channel
leakage and electromagnetic interference, this study identifies common threads
and gaps that can help guide and inform future research. Overall, the
ever-increasing reliance on sensors embedded in everyday commodity devices
necessitates that a stronger focus be placed on improving the security of such
systems against out-of-band signal injection attacks.
