# Security Challenges in Industry 4.0 PLC Systems
## 3 Risk Sources in OT Systems
### Software in Network Systems
#### 3.3.4 Other Software in Computers and Servers  
The amount of data processed and the level of advancement of applications necessary for the proper management of production in modern industrial plants can overwhelm even the most efficient computers. Therefore, industrial servers are used to handle tasks that require enormous computing power. Among the active elements in the network, we can also distinguish process computers, aimed to control the process parameters through dedicated applications (process interface) that support many different hardware environments. The issue of using PCs as elements of an industrial network is also important. The hardware of this type of equipment is of little importance from the point of view of cybersecurity. However, the greatest attention should be paid to the issue of operating systems and applications running on these systems. The most commonly used computer operating systems in industry are the Windows family and real-time systems. This is mainly caused by the requirements of SCADA, ERP or MES software producers. The popularity of Windows systems is, however, associated with the widespread information about their weaknesses and translates into the number of tools available to carry out hacker attacks. Several important aspects related to the security of computers and servers in industrial networks are listed below:  
**Firewalls**  
The term inherent in the cybersecurity of industrial network software is a firewall. It acts as a combination of hardware and software protection of the internal network against external access (public networks and the Internet). Its task is also to protect against unauthorized outflow of data from the local network to the outside. The role of a firewall can be played by a specially designed device with appropriate software or the software itself located on access points equipped with a data packet management system. The most frequently used protection techniques in a firewall is packet filtering consisting in checking their origin and managing the system of their acceptance, using algorithms for the purposes of user identification and securing programs that support certain data transmission protocols. An important function of a firewall from the cybersecurity of industrial networks point of view is the network traffic monitoring and events logging. This enables authorized persons to make early changes to the firewall configuration and makes it much easier during the risk monitoring phase. The firewall also allows to define a zone of limited trust, and thus create a subnet that isolates local servers providing services from the internal network. Industrial versions of firewalls can protect the industrial network against unauthorized access by filtering IP addresses, MAC addresses, ports dedicated to specific industrial protocols as well as monitor the correctness of the frame structure of a given protocol. However, they will not protect against data modification in a properly built frame, when it is secured only with a checksum with a well-known algorithm. **Up-to-Date Software**  
According to the CyberX report, as many as 53% of manufacturing companies still use Windows XP [70]. Lack of support for Windows XP as well as other outdated operating systems means a significant risk of hacking attacks due to the lack of further patches to prevent this type of activity. Analyzing the source code of the malware Stuxnet, it was noticed that it mainly exploited the flaws of the Windows system in order to reproduce itself on other devices. However, the problem of keeping operating systems up-to-date on PCs is complex because it depends mainly on the compatibility of the software provided by the manufacturer of the process automation equipment (allowing the creation/modification of the program). In order to update the operating system, it is necessary to verify whether the program under the given license can run on the new version of the system.