## 1 Introduction
However, the dynamic nature of network slicing introduces complex security challenges, and each slice, potentially running different services with distinct performance metrics, presents unique security needs and vulnerabilities [9]. In this context, the traditional one-size-fits-all security model is ineffectual, necessitating a paradigm shift towards more flexible, adaptive security frameworks [10]. One innovative concept in 6G technology is the \"network of networks\" (NoN) [11], which involves dynamically aggregating different networks or network segments. This aggregation enables seamless communication and resource sharing among them, thus supporting the delivery of comprehensive services [12]. In one possible implementation of NoN, network operators could assume the roles of network brokers or coordinators for different segments, including their own capacity, such as fixed access or transport connectivity, along with those provided by third parties. Client services would then be delivered as network slices, coordinated across multiple networks. This brings into play the concept of a multi-provider or multi-stakeholder, where these providers contribute their network capacity for different segments and technologies to be utilized by network operators in is integrator role. To provide secure and reliable servicesacross different network domains, network operators will require some mechanisms to establish and manage end-to-end security slices. These slices will ensure the protection of data and resources from unauthorized access and malicious attacks. Moreover, network operators will have to guarantee some Service Level Agreements (SLA) in terms of security, also known as Security SLAs (SSLA) which will specify the expected performance and quality of the security capacities. The SSLA will also define the roles and responsibilities of the different parties involved in the heterogeneous network of networks. This review explores cutting-edge network slicing security, emphasising the integration of Artificial Intelligence (AI), namely Machine Learning (ML), Software Defined Networking (SDN), and Network Functions Virtualization (NFV). These technologies are not merely enhancements to existing frameworks but pivotal to developing robust, scalable security solutions. The role of AI/ML in predictive threat detection and response transforms security from a reactive to a proactive stance, which is crucial for maintaining the integrity of real-time services. Meanwhile, SDN and NFV enable the agile implementation of security policies customized to the unique context of each slice, supporting dynamic management and orchestration of network resources. This paper aims to review the current research landscape regarding these technologies in network slicing security, assess their effectiveness, and identify research gaps and associate the research with the current findings within the 6G-OPENSEC-SECURITY ([[https://www.cttc.cat/project/secure-network-slice-manager-for-open-and-disaggregated-6g-networks/](https://www.cttc.cat/project/secure-network-slice-manager-for-open-and-disaggregated-6g-networks/)]([https://www.cttc.cat/project/secure-network-slice-manager-for-open-and-disaggregated-6g-networks/](https://www.cttc.cat/project/secure-network-slice-manager-for-open-and-disaggregated-6g-networks/)) (accessed on 29 April 2024)) project. This project aims to design and develop an intelligent and autonomous Security 6G Network Slice Manager solution for the management of network slices with security requirements in 6G multi-provider networks. Through an examination of contemporary literature, this review aims to advance the discourse on securing next-generation network architectures and propose directions for future research that will fortify the security frameworks necessary for the safe deployment of network slicing.