Wireless physical layer (PHY) secrecy has attracted much attention due to the broadcast nature of the wireless medium. To this end, researchers have been seeking new security technologies to complement physical layer security and significantly improve the overall security of wireless communication networks. In this book, the authors cover physical layer security for wireless sensing and radio environment concepts along with the related security implications in terms of eavesdropping, disruption, manipulation and, in general, the exploitation of wireless sensing by illegitimate users. After discussing the features and probabilities of wireless channels from both the communication and sensing perspectives, they cover their exploitation for secure transmission utilizing various approaches. They present various solutions from the domains of wireless communication, military radars and machine learning. Although, more emphasis on PHY security is given, other security measures are covered for the sake of completeness and as a step towards a cross-layer security and cognitive security vision.