Introduction. The article is devoted to the study of the problem of offenses in decentralized systems, in particular in blockchain networks. The author analyzes the main types of offenses that can occur in these systems, such as fraud, various attacks, and others. Since decentralized networks have no centralized control, they become more vulnerable to various types of attacks and abuses. Understanding the nature of decentralized networks can help to solve the problem of crimes in these systems more effectively, and understanding the principles of these networks can help to develop effective and transparent methods of solving such crimes. Summary of the main results of the study. Taking into account the results of the research, an explanation is provided as to how decentralized networks such as blockchain are organized, what are the offenses in such networks, what are attacks in decentralized systems. A detailed list of the main types of attacks, other types of offenses and abuses in decentralized systems is also provided, a description and explanation is provided for each type, and specific examples are also provided for some of them. Conclusions. For the first time, a list of the main offenses in decentralized networks such as blockchain has been unified and provided in the context of criminal law.