Cyber Security has become an important matter in the automation business. Schneider Electric has responded to this trend by reworking its Modbus Communication DTM for serial line and TCP. The development process followed the Microsoft security development lifecycle. This process recommends several measures from the requirements to the release phase. Examples of such measures are:
• Security and privacy risk assessment
• Attack surface analysis
• Threat modelling
• Deprecate unsafe functions
• Specific cyber security tests
The figure shows an overview of the DTM architecture. Potential points for intrusion are the interfaces between the components. These interfaces were analysed when assessing the possible threats which were classified using STRIDE (Spoofing, Tampering, Repudiation, Information disclosure, Denial of service, Elevation of privilege).This helped to define the necessary work to mitigate the threats.
After these measures were employed, the existing code base was reworked and new features were added. Improvements include the avoidance of XML vulnerabilities, data execution prevention and digital signature.
Significant effort has been invested in testing. Specific tests were defined and developed to verify the measures introduced for cyber security. Different test tools were used to cover different scenarios. Examples of these tests are:
• Prevention of adding new TCP ports during installation
• Manipulation of protocol frames
• Message overload
• Attack surface analysis
• Check of XML parser vulnerabilities
• Manipulation of setup file
The new edition of the Modbus Communication DTM for FDT1.2.x has been certified and released. The FDT2 version is in development and will be released when certification is done.
For more information and/or to download the Modbus Comm DTM, click here.
