The spread of the Internet in all areas of our lives has brought many eases and benefits for human life. Along with the development of technology, two basic issues such as security and privacy increase the importance day by day as the subjects that both individuals, institutions and governments should deal with. On the other hand, the Internet has brought along problems and threats by its nature. Risks such as the seizing and sharing of personal data without permission, and leakage of critical information for government, companies and institutions have emerged. The measures taken against individuals, institutions, companies or governments in accordance with the rules determined in the current order, and the measures taken against all kinds of threats, harassment, epidemic and disaster are called "Security". Privacy is the restriction of access to information. It means that people other than a certain person or a group cannot access this information. These two basic concepts are of great importance today. It is also very important to ensure the security and privacy of this information in today's world where the information of the organization at all levels is transmitted wired or wireless via the Internet. Otherwise, individuals, institutions and governments suffer material and moral damages. The concept of cyber security meets the reflection of security in the technology environment, which we call cyber or virtual world. People, institutions or governments want to be safe in every field. In today's world, information has gained great importance in making sense of this information and ensuring its security. Accordingly, cyber armies are set up and attacks are organized in order to damage individuals, companies, institutions and governments or to seize their information. One of the most common of these attacks is denial of service attacks from distributed sources. Although blockchain technology is not applicable in all areas and situations, it is suitable for certain applications. It offers serious advantages with its distributed structure. Blockchain technology can be used as a solution to reduce the costs of institutions, companies and governments against cyber-attacks. In this study, technical information about blockchain technology and cyber-attacks, the damages caused by cyber-attacks were shared and cost benefit analysis of blockchain, which can be used to prevent some of these attacks in certain cases, was made. This is the first of the motivation points of this study. The second issue is the material and moral consequences of security and privacy violations. This study will focus more on material losses. Especially the financial losses of companies and governments will be evaluated. It is obvious that blockchain technology provides significant gains in terms of security and privacy in the areas where it can be used due to its distributed structure. The final motivation point of the study is the financial gains that this distributed structure will provide for institutions and governments. After the first section, which contains general information about cyber security and blockchain, in the second section, cyber-attacks made in the past are mentioned and the damages arising are given. Afterwards, examples of applications where blockchain technology can be used are given and the gains offered in terms of security are evaluated. Finally, financial analysis of these gains was made. The aim of this study is to analyse the blockchain technology that can provide significant gains in various financial application areas, to emphasize the importance of cyber security for companies and countries. As we know, we can classify the costs that may be encountered in using an information system as follows. Prevention Costs: System malfunction, disruption, virus infection, cyber-attack etc. in terms of situations such as all kinds of protective and preventive activities. Measurement Valuation Cost: These are the activities aimed at measuring the quality to determine whether the IT system produces reliable and quality (accurate, usable, timely) information. Internal Failure Cost: Costs caused by producing incorrect information due to errors, defects, and malfunctions that arise during the information production system, and the costs created during the correction of false information are internal failure costs. External Failure Costs: Damages, damages and compensations that arise due to the use of the wrong information by the information user after the (wrong) information produced by the data processing unit is transferred to the information user. As in almost every sector, it will be necessary to pay attention to the costs of prevention and endure in order to prevent failures (internal, external) in the information system. Due to the risks posed by cyber security developing technology, it will be one of the most important and popular topics of the coming period as it is today. Along with security, it is also important to protect personal and corporate privacy. All of these are also the risks faced by states. Many cyber-attacks, which have been and continue to be experienced, have caused systems to stop, damage or disappear, and thus individuals, institutions and states have also suffered material and moral damages. Spiritual damages also have material consequences. So much so that people who are morally damaged bring compensation cases to the owners of the systems infiltrated by the attackers, and material obligations arise in this way. In addition, the attacked institutions and states are also exposed to financial losses directly. Since this situation causes serious financial losses, individuals, institutions, companies and governments should increase their investments in order to ensure cyber security and privacy and prefer safe and robust systems. Although security expenditures are not considered important in terms of investment costs, it is a fact that those who are attacked have to pay many times more of these investments. In the light of all this information, it has been determined that the blockchain technology, whose technical details and usage areas are given, offers great advantages for a safe system. Blockchain system is not a miraculous system that can be used in every field and in every system. It is suitable for certain areas and promises to guarantee immunity, security and privacy in the areas where it is used. In this study, the benefits of using this technology for a company in a field where blockchain can be applied were evaluated in terms of cost. As a result, it has been determined that it saves companies from various cost items in terms of cost and reduces the costs of companies in the general table
