Cryptocurrency is a novel exploration of a form of currency that proposes a decentralized  electronic payment scheme based on blockchain technology and cryptographic theory. While blockchain has the security characteristics of being distributed and tamper-proof, increasing market demand has led to a rise in malicious transactions and attacks, thereby exposing cryptocurrency to vulnerabilities,  privacy issues, and security threats. Particularly concerning are the emerging types of attacks and threats, which have made securing cryptocurrency increasingly urgent. This paper classifies existing cryptocurrency security threats and attacks into five fundamental categories based on the blockchain infrastructure, and it analyzes in detail the vulnerability principles exploited by each type of threat and attack. Furthermore, the paper examines the attackers’ logic and methods and provides insights that enable easy reproduction of the vulnerabilities. We also summarize and evaluate existing detection and defense solutions, offering important references for ensuring cryptocurrency security. Finally, the paper discusses the future development trends of cryptocurrency.