# Security and Privacy in Physical-Digital Environments: Trends and Opportunities
## 1 Introduction  
The growing integration of technology into everyday life has fueled the rapid evolution of the Internet and digital communications, reshaping human-computer interaction (HCI). Over time, the Internet has transitioned from a mere communication tool to a ubiquitous presence, embedding itself deeply in daily activities. Information exchange now transcends human interactions, extending to machine-to-machine communications on an unprecedented scale.  
[PERSON] and [PERSON]'s 1994 groundbreaking paper [1] marked the introduction of the term Mixed Reality(MR). This pioneering concept combines the physical and virtual worlds within the virtuality continuum [2] in the same visual display environment, encompassing Augmented Reality (AR), Augmented Virtuality (AV), Virtual Reality (VR), and any technology that allows interactions between digital material and real-world objects.  
The technological advancements of these systems within the spectrum have enabled the creation of immersive technologies, which has led to the emergence of the _Metaverse_. In 1992, [PERSON] introduced the Metaverse in his novel \"Snow Crash\" [3]. According to [PERSON], the Metaverse is a virtual environment that runs parallel to the physical world and allows users to interact with each other through digital avatars. It is a virtual reality space where users can engage in several activities, including gaming, socializing, and commerce. It is a shared, persistent environment that allows users to create andcustomize their digital representations or avatars, through which users can interact with each other in real time.  
While these innovations present unprecedented opportunities, they also introduce complex security, privacy, and confidentiality challenges. As physical-digital environments like MR and the Metaverse evolve, they become targets for novel threats and vulnerabilities. By addressing the intersection of security, privacy, and immersive technologies, this paper sheds light on the opportunities and risks in physical-digital environments, offering a roadmap for future advancements and challenges.  
Therefore, the following research questions are posed:  
* RQ1--What are the leading security risks stemming from the development and expansion of Metaverse and Mixed Reality technologies?
* RQ2--How can a user's privacy be maintained in the context of involving and participatory experiences in the Metaverse and Mixed Reality environments?
* RQ3--What are the ethical issues related to the collection, utilization, and distribution of data in Metaverse and Mixed Reality technologies, and how can these issues be mitigated?  
A comprehensive search was conducted to support answering these questions. Keywords like \"Metaverse\", \"Mixed Reality\", \"Augmented Reality\", \"Augmented Virtuality\", \"Virtual Reality\", \"security\", \"privacy\", \"confidentiality\", \"threats\", \"vulnerabilities\", and \"countermeasures\" were among the many terms utilized to run the search in the multiple available databases, including Scopus, Web of Science, Google Scholar, MDPI, and IEEEXplore. Following this, data extraction was conducted using a standardized extraction form to capture key information, including author(s), publication year, research methodology, findings, and conclusions. Then, we conducted a thematic analysis to identify and organize significant themes and patterns within the selected literature.  
The remainder of this paper is organized as follows. The next section introduces concepts related to MR and the Metaverse, describes their architecture, and presents application areas. Section 3 identifies potential attack vectors and discusses threats and countermeasures. Section 4 delves into challenges and possible solutions. Section 5 discusses research findings and outlines future research directions in securing and protecting these environments. Finally, Section 6 concludes the paper.