Abstract
With the rise of the metaverse, its security risks are of great concern. We have researched the literature related to metaverse security in recent years and summarised the security risks of metaverse at the technological level. First, we introduce the concept of the metaverse and the role of the five underlying technologies (blockchain, Internet of Things, cloud services, artificial intelligence, and digital twins) in the metaverse. Then, based on the security risks and countermeasures of these underlying technologies themselves, we summarise the security issues faced by the metaverse. Finally, we summarise the opportunities and challenges of metaverse security from the perspectives of the five underlying technologies and the overall perspective of the metaverse.