Stuart Madnick, a professor of information technology at the Massachusetts Institute of Technology and the founding director of cybersecurity at the Massachusetts Institute of Technology's Sloan Research Consortium, recently published an article in the Wall Street Journal that the blockchain is not as secure as it is alleged. The MIT study analyzed 72 publicly reported security breaches in the blockchain system between 2011 and 2018. Among them, the main vulnerabilities include transparency, distributed control and anonymity, which is also the main advantage of blockchain technology. Madnick said that while transparency allows people to view the software and confirm that there are no defects, it is said to allow malicious users to easily access and explore to find defects that others have not observed. As for anonymity, Madnick emphasized that if the key is lost, access to the user blockchain account cannot be restored. Madnick's conclusion is that, most importantly, although the blockchain system represents an advancement in encryption and security, it is somewhat vulnerable to attacks as well as other technologies, and blockchains have new vulnerabilities. In fact, human behavior or inaction still has a major impact on blockchain security.