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Abstract: Supervisory Control and Data Acquisition (SCADA) and other industrial control systems (ICS) are used to monitor and control industrial systems such as refineries, trains, water and sewage systems, plants, factories, and the electric grid. Typically, they are dispersed over a wide geographical area and managed from a centralized supervisory site. These systems control real physical equipment that, if not controlled correctly, can cause significant physical, economic, and environmental damage. Many of these systems are critical to the infrastructure of a nation state, a region, or a company. They have become cyber-targets by agents of various military, criminal, and political organizations as well as terrorists, malcontents, and others. The programmable logic controller (PLC) is the workhorse of SCADA and other control systems. It normally receives data from sensors and other input devices which is then used to programmably control switches, actuators, pumps, motors and other such devices to interact physically with its environment in a safe and reliable manner. This small and rugged computer maintains programmable control over machinery and equipment that is often located in unmanned, remote, and inhospitable environments. Stuxnet and other cyber-attacks have drawn research attention seeking to protect a vulnerable centralized supervisory site but there has been little academic cyber-security research into defending the remote PLC, or the fieldbus network upon which it operates. This paper surveys and classifies recent research efforts to attack or defend programmable logic controllers and fieldbus networks. In addition, we frame additional research that could potentially lead to better cyber-protection of supervisory control and data acquisition (SCADA) systems.
Keywords: PLC, ICS, SCADA, security, network security, software vulnerability mitigation, fieldbus
1. Introduction
Well known attacks on Supervisory Control and Data Acquisition (SCADA) systems include the 2010 attack upon the Iranian nuclear program by Stuxnet (Failliere, Murchu and Chien 2011), the 2015 attack upon the Ukrainian power grid (SANS ICS and E-ISAC 2016), and the Maroochy Water System attack in 2000 (Miller and Rowe 2012). Presidential Executive Order 13636 (Office of the President of the United States 2013) names cyber-threats to our critical infrastructure as a serious national security challenge and classifies the cyber defence of these systems as a national priority.
SCADA systems are hierarchical in nature with sensors and actuators that interact with field control...