Security threats on Blockchain and its countermeasures

1Dept. of Computer Engineering, Vidyalankar Institute of Technology, Maharashtra, India 2Dept. of Computer Engineering, Vidyalankar Institute of Technology, Maharashtra, India ----------------------------------------------------------------------***--------------------------------------------------------------------Abstract Blockchain, the foundation of Bitcoin, has become one of the most popular technologies to create and manage digital transactions recently. It serves as an immutable ledger which allows transactions take place in a decentralized manner. This expeditiously evolving technology has the potential to lead to a shift in thinking about digital transactions in multiple sectors including, Internet of Things, healthcare, energy, supply chain, manufacturing, cybersecurity, and principally financial services. However, this emerging technology is still in its early stage of development. Despite the huge opportunities blockchain offers, it suffers from challenges and limitation such as scalability, security, and privacy, compliance, and governance issues that have not yet been thoroughly explored and addressed. Although there are some studies on the security and privacy issues of the blockchain, they lack a systematic examination of the security of blockchain systems. This paper conducted a systematic survey of the security threats to the blockchain systems and reviewed the existing vulnerabilities in the Blockchain. These vulnerabilities lead to the execution of the various security threats to the normal functionality of the Blockchain platforms.