  Security has emerged as one of the critical requirements in future wireless
networks. Unlike traditional cryptography-based security, physical layer
security (PLS) exploits various features of the random wireless channel to
secure not only the information being communicated but the whole communication
process from any type of attack. Future wireless networks are envisioned to
feature new technologies such as re-configurable intelligent surfaces, massive
multiple input multiple output, and sensing, to accommodate the emerging
use-cases. Both, the new technologies and the new use-cases have been found to
enrich the channel characteristics by unveiling some new channel features which
can be readily exploited to facilitate PLS. This article surveys these new
channel features to reveal their potential for PLS implementation. In the
course of the article, the assessments of important qualities while selecting a
certain channel feature for the PLS application are discussed. The importance
of the channel control concept and sensing technologies that facilitate the
accessibility of certain channel features are highlighted from the PLS
perspective. Security attacks aimed at channel characteristics, rather than the
communication itself, in order to disrupt PLS implementations are also
discussed. Finally, the article summarizes the possible research direction for
channel-based PLS.
