  Integrated sensing and communication (ISAC) has recently emerged as a
candidate 6G technology, aiming to unify the two key operations of the future
network in spectrum/energy/cost efficient way. ISAC involves communicating
information to receivers and simultaneously sensing targets, while both
operations use the same waveforms, the same transmitter and ultimately the same
network infrastructure. Nevertheless, the inclusion of information signalling
into the probing waveform for target sensing raises unique and difficult
challenges from the perspective of information security. At the same time, the
sensing capability incorporated in the ISAC transmission offers unique
opportunities to design secure ISAC techniques. This overview paper discusses
these unique challenges and opportunities for the next generation of ISAC
networks. We first briefly discuss the fundamentals of waveform design for
sensing and communication. Then, we detail the challenges and contradictory
objectives involved in securing ISAC transmission, along with state-of-the-art
approaches to address them. We then identify the new opportunity of using the
sensing capability to obtain knowledge of the targets, as an enabling approach
against known weaknesses of PHY security. Finally, we illustrate a low-cost
secure ISAC architecture, followed by a series of open research topics. This
family of sensing-aided secure ISAC techniques brings a new insight on
providing information security, with an eye on robust and hardware-constrained
designs tailored for low-cost ISAC devices.
