# Security Challenges in Industry 4.0 PLC Systems
## 3 Risk Sources in OT Systems
### Software in Network Systems
#### 3.3.3 Hmi  
Human-Machine Interface (HMI) is an industrial interface between a machine or process and the operator. By using the HMI, it is possible to influence the course of the process and its control in a more friendly environment than the set of PLC registers. Modern operator panels can be remotely controlled. They are also equipped with software and touch screens, which greatly facilitates the exchange of information at the human-machine level. The task of the HMI is to provide the operator with up-to-date, real information in a form that allows to make the best decision at a given moment of machine operation. The SCADA system is more complex and has a more extensive visualization of the entire process compared to HMI panels. The HMI panel is usually used for communication with individual devices. The SCADA system collects data from all devices that have a significant impact on the process and visualizes this data in one place, creating a comprehensive collection of all available information about the process.  
The most important threats considered in the context of HMI is authorization management. Often, different levels of access are created on the machines, depending on the operator's rights, in order to protect against unauthorized changes to the parameters of the production process. According to the SANS report, in 89% of cases, such separation takes place using a different level of passwords [86]. However, providers of equipment and the environment that allows the creation of HMIs most often save passwords in the memory registers of operator panels, which are not secured by any encryption method or simply force the storage of passwords in the memory of the PLC controller, and thus handling the authorization request from its level. Assuming that the operator panel communicates with the PLC using one of the known communication standards (e.g., Ethernet), it is not difficult to imagine a way to carry out an attack using the data obtained through the MIM listening device. In addition, it is worth considering the case in which SCADA has full access to the operator panel registers in accordance with the priority of its control, which may lead to distributed hacking attacks on the level of the entire industrial network system.  
Another source of problems related to HMIs is the lack of an encrypted connection with the controllers, which is most often based on data transmission protocols used according to industrial standards. This is because software producers strive to standardize the services offered in order to ensure compatibility with as many devices and external programs as possible. The use of this type of unsecured connection allows to carry out successful MIM attacks and simulate the operation of any of the elements by transmitting a previously modified intercepted communication frame.  
According to the report prepared by TrendMicro [89], as much as 20% of the identified threats from HMI refer to the lack of security in the operator panels' memory and software. Often the way the memory is built in the operator panels forces the integrators team to implement the simplest memory management mechanisms, defined by the programming environment offered by the manufacturer. The main element to consider when designing HMI is the method of securing the code and security related to reading and writing data that go beyond the defined range.