I. Introduction  
A. Challenges for Securing Metaverse  
B. Related Works  

II. An Overview of Metaverse  
A. Existing Metaverse-Related Standards  
B. Metaverse Architecture  
C. Key Characteristics of Metaverse  
D. Enabling Technologies of Metaverse  
E. Existing Modern Prototypes of Metaverse Applications  

III. Threats and Countermeasures  
A. Threats to Authentication in Metaverse  
B. Threats to Access Control in Metaverse  

IV. Threats and Countermeasures to Data Management in Metaverse  
A. Threats to Data Management in Metaverse  
B. Security Countermeasures to Metaverse Data Management  

V. Privacy Threats and Countermeasures in Metaverse  
A. Privacy Threats in Metaverse  
B. Privacy Countermeasures in Metaverse  

VI. Network-Related Threats and Countermeasures in Metaverse  
A. Threats to Metaverse Network  
B. Situational Awareness in Metaverse  

VII. Economy-Related Threats and Countermeasures in Metaverse  
A. Threats to Metaverse Economy  
B. Open and Decentralized Creator Economy  

VIII. Threats to Physical World and Human Society and Countermeasures in Metaverse  
A. Threats to Physical World and Human Society  
B. Physical Safety  
C. Society Management  

IX. Governance-Related Threats and Countermeasures in Metaverse  
A. Threats to Metaverse Governance  
B. Digital Governance in Metaverse  

X. Future Research Directions  
A. Endogenous Security Empowered Metaverse  
B. Cloud-Edge-End Orchestrated Secure Metaverse  
C. Cross-Chain Interoperable and Regulatory Metaverse  
D. Energy-Efficient and Green Metaverse  
E. Content-Centric and Human-Centric Metaverse  

XI. Conclusion