ABSTRACT In modern cyber-physical systems, there is a high degree of connectivity that is imperative to satisfy the Four Industrial Revolution paradigm (Industry 4.0). While creating new systems according to the Industry 4.0, there are several protocols and solutions that can be applied. However, the introduction of Industry 4.0 to the existing industrial systems is not so straightforward. One point of consideration is the necessity of system modification, and another is the potential security threats a system could face. A solution presented in this paper addressing these issues is a FPGA-based network analyser with network datagram filtering and process data extraction. The analyser is transparent and may be applied without alterations to the monitored system. Moreover, there is no risk of influencing the system operation either by the data extraction device itself or by unauthorised access from the Internet, because the FPGA is a passive device operating as a data diode. The presented solution allows for the integration of existing Ethernet-based systems with cloud services for further processing of the data obtained from the monitored system. The FPGA makes process data available for the enterprise information systems.