The article examines cybersecurity in networks supporting card payment systems, which serve as a distributed critical infrastructure characterized by high transaction volumes, dense data concentration, and escalating cyber threats. The study aims to conceptualize the payment card environment not merely as a set of isolated components, but as interdependent domains of trust through which a single transaction simultaneously traverses terminals, gateways, processors, schemes, and issuing and acquiring banks. The relevance is grounded in the structural dominance of card payments in retail and remote commerce, the documented growth of ransomware, data exfiltration, and DDoS campaigns against financial institutions, as well as the tightening regulatory focus on cardholder data protection and operational resilience. The novelty of the work lies in its tri-layered analytical design, which combines the architectural decomposition of the payment chain, a normative–taxonomic reading of PCI DSS concepts related to cardholder data, sensitive authentication data, and controlled environments, and a threat-oriented mapping of prevalent attack classes onto this architecture. This perspective enables the authors to demonstrate that excessive network connectivity and poorly defined trust boundaries simultaneously expand the formal scope of compliance and increase the number of lateral movement paths for attackers. The main conclusions emphasize the necessity of multi-layer, mutually constraining security controls, strict access and privilege management, cryptographic governance, environmental minimization, zero–trust–oriented segmentation, and response capabilities, where time to detection and recovery becomes the decisive parameter. The article will be particularly useful for payment system architects, banking cybersecurity practitioners, regulators, and researchers in the field of financial infrastructure resilience.