The increasing adoption of IoT devices has raised significant concerns about security and privacy. This paper proposes a blockchain-based approach for anomaly detection and intrusion prevention in IoT networks. The methodology combines blockchain technology with anomaly detection algorithms to enhance the security and trustworthiness of IoT systems. Through simulations and experiments using real-world IoT datasets, the effectiveness of the approach is evaluated. The results demonstrate improved accuracy in detecting anomalies and reduced false positives compared to traditional methods. The blockchain-based solution also provides tamper-proof and decentralized data storage, ensuring the integrity and availability of IoT network information. This research highlights the potential of blockchain technology as a robust solution for enhancing anomaly detection and intrusion prevention in IoT networks, addressing critical security challenges in the IoT ecosystem.