Cyber-Resilient SCADA Systems via Secure State Restoration

Abstract

Supervisory Control and Data Acquisition (SCADA) systems are widely used by critical infrastructure and are ubiquitous in numerous industries including telecommunications, gas, and manufacturing. SCADA systems are high risk targets for cyber attack given their criticality, interconnectedness, and internet accessibility. Programmable Logic Controllers (PLCs) are one of the primary components of SCADA systems which monitor and provide control instructions to other devices, as well as receive data from sensors. Unfortunately, PLCs today are configured in a persistent manner, i.e. physical devices are configured once and designed to be continuously operational, and are ill-suited to operate in a virtual, dynamic, and cyber resilient environment. Therefore, there is a need for cyber resilient SCADA architectures which can endure and recover from cyber attacks. The presented approach describes a secure way to store system states which are then used by redundant, non-persistent devices during operation and recovery procedures. Successful application of the approach results in a non-persistent, Byzantine fault tolerant, virtual Industrial Control System (ICS) where state and function can be stored and restored securely, resulting in greater system cyber resilience. To demonstrate the efficacy and assess the applicability of the approach, mathematical and timing analyses were conducted. An environment implementing the approach architecture was configured and tested where a cyber attack against non-persistent PLCs resulted in quick identification and subsequent secure restoration with no loss in state or functionality. This approach works as a practical framework for applying cyber resilience with non-persistence and state restoration to SCADA environments.