  The Open Radio Access Network (Open RAN) framework, emerging as the
cornerstone for Artificial Intelligence (AI)-enabled Sixth-Generation (6G)
mobile networks, heralds a transformative shift in radio access network
architecture. As the adoption of Open RAN accelerates, ensuring its security
becomes critical. The RAN Intelligent Controller (RIC) plays a central role in
Open RAN by improving network efficiency and flexibility. Nevertheless, it also
brings about potential security risks that need careful scrutiny. Therefore, it
is imperative to evaluate the current state of RIC security comprehensively.
This assessment is essential to gain a profound understanding of the security
considerations associated with RIC. This survey combines a comprehensive
analysis of RAN security, tracing its evolution from 2G to 5G, with an in-depth
exploration of RIC security, marking the first comprehensive examination of its
kind in the literature. Real-world security incidents involving RIC are vividly
illustrated, providing practical insights. The study evaluates the security
implications of the RIC within the 6G Open RAN context, addressing security
vulnerabilities, mitigation strategies, and potential enhancements. It aims to
guide stakeholders in the telecom industry toward a secure and dependable
telecommunications infrastructure. The article serves as a valuable reference,
shedding light on the RIC's crucial role within the broader network
infrastructure and emphasizing security's paramount importance. This survey
also explores the promising security opportunities that the RIC presents for
enhancing network security and resilience in the context of 6G mobile networks.
It outlines open issues, lessons learned, and future research directions in the
domain of intelligent control in 6G open RAN, facilitating a comprehensive
understanding of this dynamic landscape.
