Security and privacy in multi-cloud and hybrid cloud environments: Challenges, strategies, and future directions

The rapid adoption of multi-cloud and hybrid cloud environments has revolutionized modern computing by enhancing scalability, flexibility, and cost-efficiency. However, these environments introduce significant security and privacy challenges due to the distributed nature of data storage, heterogeneous infrastructures, and intercloud communications. This review comprehensively examines the critical security and privacy concerns associated with multi-cloud and hybrid cloud architectures, including data confidentiality, access control, secure communication, regulatory compliance, and emerging attack vectors such as cross-cloud threats and side-channel attacks. We analyze existing security strategies, including cryptographic techniques, identity and access management (IAM) mechanisms, AI-driven threat detection, and privacy-preserving methodologies. Furthermore, we provide a comparative evaluation of these approaches, highlighting their trade-offs in terms of security effectiveness, computational overhead, and deployment feasibility. In addition, we explore emerging trends such as post-quantum cryptography, zero-trust architectures, decentralized security frameworks, and AI-powered security automation to mitigate evolving threats. Finally, we outline open research challenges and future directions, emphasizing the need for scalable, adaptive, and regulation-compliant security solutions. This review serves as a foundation for researchers and practitioners aiming to enhance security and privacy in multi-cloud and hybrid cloud infrastructures, ensuring robust and resilient cloud computing ecosystems.