![]() Real-Time support is a requirement mainly for devices at the field level (e.g., sensors and actuators).Įxample of Modbus Network Architecture. Although Modbus TCP/IP as a protocol could support communication between field devices via TCP, i.e., between sensors, actuators and PLCs, at this point there is an additional requirement: The behavior as a real-time system (RTS). However, Modbus TCP/IP is mostly used in the data sharing between the field device level (e.g., PLC, CAN J1939 to the Modbus Gateway) and the SCADA system level. The Modbus protocol is part of the first two levels of this layered model. The Figure 1 allows identifying action fields of Modbus based on the ISA 95 model and related standards. Every type of device (PLC, HMI, Control Panel, Driver, Motion control, I/O Device, and so on) can use the Modbus protocol to initiate a remote operation. The Modbus protocol allows an easy communication within all types of network architectures. Modbus is a request/reply protocol, and offers services specified by function codes. ![]() The Internet community can access Modbus at a reserved system port 502 on the TCP/IP stack. Modbus has been known as industry’s serial de facto standard since 1979 and keeps on enabling millions of automation devices to communicate. Modbus is an application layer message exchange protocol, which provides client-server communication between devices connected on different sorts of buses or networks. For this purpose, different latencies measurements in industrial environments are used as a benchmark, which are matched against the latencies in our proposal for different cipher suites. Then both the client and the server are deployed over this network in order to verify the feasibility of the proposal. This testnet has been designed based on an industrial security standard, such as IEC-62443, which divides the industrial network into levels. Finally, our performance analysis involves deploying our design over a testnet built on GNS3. The security analysis involves verifying the protocol’s resistance to different types of attacks, as well as that certain pillars of cybersecurity, such as integrity and confidentiality, are not compromised. Our proposal is evaluated through two approaches: A security analysis and a performance analysis. This model is divided into an authorization process via roles, which is inserted as an arbitrary extension in the certificate X.509v3 and the message authorization via unit id, a unique identifier used to authorize the Modbus frame. From the security specifications, this study addresses the security problems of the Modbus protocol, proposing a new secure version of a role-based access control model (RBAC), in order to authorize both the client on the server, as well as the Modbus frame. The security features leverage X.509v3 digital certificates for authentication of the server and client. TLS will encapsulate Modbus packets to provide both authentication and message-integrity protection. In order to provide security mechanisms to the protocol, the Modbus organization released security specifications, which provide robust protection through the blending of Transport Layer Security (TLS) with the traditional Modbus protocol. The exploitation of such flaws may greatly influence companies and the general population, especially for attacks targeting critical infrastructural assets, such as power plants, water distribution and railway transportation systems. This issue enables certain types of attacks, for example, man in the middle attacks, eavesdropping attacks, and replay attack. Unfortunately, Modbus lacks basic security mechanisms, and this leads to multiple vulnerabilities, due to both design and implementation. ![]() Modbus is an application protocol that allows communication between millions of automation devices. Industrial Control Systems (ICS) and Supervisory Control systems and Data Acquisition (SCADA) networks implement industrial communication protocols to enable their operations.
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