From Perimeter to Posture: Securing Physical Devices in IoT with Adaptive Cyber Defense

The rapid proliferation of the Internet of Things (IoT) has transformed digital ecosystems, enabling pervasive connectivity across industries, healthcare, smart homes, and financial infrastructures. However, the physical devices that underpin IoT ecosystems remain highly vulnerable, often constrained by limited computational capacity and weak native security mechanisms. Traditional perimeter-based defenses, designed for static enterprise networks, fail to address dynamic device-level threats, insider risks, and sophisticated adversarial tactics. This paper proposes a posture-centric adaptive cyber defense framework that leverages Zero Trust principles, Network Access Control (NAC), and Artificial Intelligence (AI)-driven anomaly detection to safeguard physical IoT devices. A mixed-methods approach, combining systematic literature review, architecture modeling, and simulated threat scenarios, was employed to evaluate the framework. Findings reveal that posture-based continuous validation enhances resilience by reducing insider risks, mitigating device-level compromise, and automating incident response. By shifting from perimeter-based to posture-centric defense, this study contributes a scalable, adaptive, and intelligence-driven security model essential for future-proofing IoT ecosystems.