The Internet of Things (IoT) continues to reduce human involvement in daily operations while accelerating the digitalization of various aspects of life. As IoT device applications rapidly expand, the volume of shared and generated data has significantly increased. However, due to the inherent limitations in the architecture of IoT devices, securing locally stored data and ensuring the reliability of data shared across devices has become increasingly challenging. Traditional security measures have proven insufficient in addressing these concerns. In response to the growing need for confidentiality and trust, researchers and cybersecurity analysts have turned to blockchain technology for securing IoT networks. Blockchain, with its decentralized and distributed database architecture, offers a trusted and consistent infrastructure for IoT systems. Its core features—immutability, transparency, authentication, authorization, and secure distributed data storage—enhance the security of data collected from IoT devices. This study provides an in-depth examination of blockchain-based IoT networks. It reviews recent advancements, outlines the current state of research, discusses ongoing challenges, and highlights promising directions for future development. A comprehensive survey of state-of-the-art studies in this field is also presented.