Human cognitive capacities and the needs of human-centric solutions for “Industry 5.0” make humans an indispensable component in Cyber-Physical Systems (CPSs), referred to as Human-Cyber-Physical Systems (HCPSs), where AI-powered technologies are incorporated to assist and augment humans. The close integration between humans and technologies in Sect. 1.1 and cognitive attacks in Sect. 1.2.4 poses emerging security challenges, where attacks can exploit vulnerabilities of human cognitive processes, affect their behaviors, and ultimately damage the HCPS. Defending HCPSs against cognitive attacks requires a new security paradigm, which we refer to as “cognitive security” in Sect. 1.2.5. The vulnerabilities of human cognitive systems and the associated methods of exploitation distinguish cognitive security from “cognitive reliability” and give rise to a distinctive CIA triad, as shown in Sects. 184.108.40.206 and 220.127.116.11, respectively. Section 18.104.22.168 introduces cognitive and technical defense methods that deter the kill chain of cognitive attacks and harden the cognitive security. System scientific perspectives in Sect. 1.3 offer a promising direction to address the new challenges of cognitive security by developing quantitative, modular, multi-scale, and transferable solutions. Figure 1.1 illustrates the structure of Chap. 1.