PLCs are an essential part of any production line and as we move deeper into the fourth industrial revolution, more internet-connected sensors and systems are interfacing with PLCs. This exposes the complete system to cyber-attacks that are difficult to predict and can lead to complete system failure, life endangerment, and financial loss. To mitigate this, designers should take preventative measures at both the hardware and software level to protect PLCs and other connected devices in the factory.
Common Security Attacks
Table 1. shows common security attacks on a PLC system including local attacks such as PLC reprogramming via a flash drive or SD card and remote attacks such as man-in-the-middle that hide potential faults in production. For example, in a food and beverage manufacturing facility producing ingredients for chocolate or baking, it is essential to track all chemicals in a mixture and monitor key events such as a faulty boiler. A man-in-the-middle attack that hides potential faults can result in erroneous mixtures unbeknownst to the operator.
PLC Design with Security Features
NXP has developed a broad portfolio of scalable security solutions that provide a foundation for achieving the most effective security levels based on the potential security attacks on a system. Figure 1. shows a Micro Safety PLC solution that addresses the attacks shown in Table 1.
The LPC55S6x MCU incorporates software-based security based on ARM TrustZone (TZ), which enables a secure and isolated execution environment that handles trusted operations including communication to external memory and software updates. To further isolate protected operations, the SE050 secure element provides support of main TPM functionalities including physical isolation that protects master keys, tamper resistant protection, and software authentication. It also creates a secure channel for data transfer to the MCU.
The combination of the LPC55S6x MCU and SE050 secure element provide a countermeasure to maximize security and maintain system integrity throughout the lifecycle of the PLC. This minimizes system downtime and critical information leakage that promotes safety and quality.
Additional steps can be taken to mitigate security attacks such as regular updates to antivirus software to reduce malware injection instances, appropriately manage access level to PLCs by personnel and only allow certain PCs to be used for programming.