# Analysis of Security Issues and Countermeasures for the Industrial Internet of Things
## 2 IIoT Architecture
The middleware layer is introduced to provide a more flexible association between the hardware devices and effective communications to various applications by enabling real-time information flow. In [50], the authors propose another five-layer IoT architecture. These layers are objects, object-abstraction, service management, application, and business manage ment layers. The newly provisioned business management layer is the topmost layer of the architecture. It controls IoT system activities and manages services using dedicated business models applied to the received data from the service management layer (through the application layer). In proposal [51], authors illustrate a relationship between a three-layer (e.g., [52]) and a five-layer (e.g., [50]) IoT architectures. In comparing these architectures, the authors argue that the object and the object abstraction layers in a five-layer architecture are the same as the perception and network layers in a three-layer architecture, where the application layer in a three-layer architecture is composed of the core functionality compounding of the service management layer, application layer, and business management layer of a five-layer architecture. CISCO provides a seven-layer IoT reference architecture [53]. From bottom to top, these layers are physical devices and controllers, connectivity, edge (fog) computing, data accumulation, data abstraction, applications and collaboration, and processes. For IIoT, a three-layer architecture is discussed in [5]. The layers are sensors, networks, and services. Another three-layer architecture for IIoT is discussed in [38]. Unlike [5], it is composed of physical, communication, and application layers. Proposal [36] discusses a four-layer IIoT architecture composed of thing, network, middleware, and application layers. The newly introduced middleware layer is the central point of the architecture that consists of different applications, middleware services, databases, and management software. In [54], a four-layer IIoT architecture is presented. These layers are perception fog, cloud, and application layers. Fog layer has been introduced to minimize the latency in decision making at the edge devices, consider the resource-constraint nature of the devices, and improve battery life of the devices in offloading the intensive computations. Another four-layer IIoT architecture is presented in [39], composed of perception, network, support, and application layers. The functioning of the support layer can be regarded as a data layer performing data analytics tasks. In [37], a five-layer IIoT architecture is discussed. The first layer is composed of embedded devices, sensors, and actuators. The second layer is composed of Distributed Control Systems (DCS), Programmable Logic Control (PLC), and Gateways. The third layer is composed of SCADA systems. The fourth layer is composed of office applications, Intranet services, Web services, etc. Finally, the fifth layer is composed of enterprise applications, and cloud computing services. In Figure 3, we present an outline of three distinct IIoT layer architecture (three-layer [5], four-layer [39], and five-layer [37]) discussed above. We argue that an layered IIoT architecture must support an industrial platform's scale and diverse nature of connected objects, applications, and associated services. At the same time, the architecture must be flexible to collect contextual information, store processed data, analyze the operation and detect anomalies, visualize the performance, and execute the instruction with high efficiency. The architecture also needs to handle the essential elements in traditional information security, i.e., communication, control, and computation [55]. We argue that an ideal view of an IIoT architecture should contain the different requirements of the IIoT system, and simultaneously fulfill the dynamic nature of the system.