A Comprehensive Review of Cybersecurity Threats, Vulnerabilities, and Mitigation Techniques in the Internet of Things (IoT)
Internet of Things (IoT) has become a new paradigm that combines physical devices with computing and networking features to form intelligent systems that can accomplish their tasks with minimal human interaction. It is estimated that by 2030, there will be more than 30 billion interconnected IoT devices, which will transfer more than 40 zettabytes of data each year. Nevertheless, this exponential increase has brought surprising cybersecurity issues, and recent evaluations show that over 70% of IoT devices are susceptible to hacking. This review examines the complex security environment of IoT ecosystems, evaluates vulnerabilities at each layer of architecture, explores new threat vectors, and assesses new defense solutions. This paper introduces a systematic review of IoT security issues based on a five-layer architecture and specifically focuses on the vulnerabilities of the network and application layers. It examines the ways in which artificial intelligence, blockchain technology, edge computing, and Zero Trust Architecture will transform IoT security paradigms. This review helps reveal long-standing issues such as resource limitations, device heterogeneity, and scaling challenges through the analysis of actual attack cases and defenses in the field of smart healthcare, industrial IoT, smart cities, and other vital infrastructures. Recommendations on future research directions are then given at the end of the paper with an emphasis on quantum-resistant cryptography, 6G network security, and standardized security frameworks required to construct resilient IoT ecosystems.