The aim of this bachelor thesis was to theoretically describe the non-encrypting ransomware and encrypting ransomware, usage of Bitcoin cryptocurrency in a viral attack and to explain the process of hashing within the file protection system. By comparing the most frequently used file backup systems, it was concluded that they do not operate like a classic backup system should. It is necessary to create a file backup and restoration system in which it is possible to create copies of files with specific file extensions and to enable their restoration. By comparing hash values of a file, a change within the file can be detected. The system checks the hash value of the selected document and compares them with the values in its database. If the result of the search is negative, the system creates a copy of the selected file and a new entry in the database. With that, the system enables restoration of different versions of the file, avoiding data loss. The application was made in C# programming language.