Towards a Standard for Highly Secure SCADA Systems

The critical energy inkstructures include gas, OL and electric power. These Mrastructures are complex and interdependent nmvorks that are vital to the national secwiy and social well being of our nation. Many electric power systems depend upon gas and oil, while fossil energy delive~ systems depend upon elecnic power. The control mechanisms for these Mrastructures are often referred to as SCADA (Supmivry CkmdandDaU Ac@itz&z) systems. SCADA systems provide remote monitoring and centralized control for a distributed tmnsportation infmsmucture in order to facilitate delivery of a commodi~. AIthough many of the SCADA concepts developed in this paper can be applied to automotive mmsponation systems, we will use transportation to refer to the movement of electrici~, gas, and oil. \ Recently, there have been seveml reports suggesting that the widespread and increasing use of SCADA for control of energy systems provides an increasing opportuni~ for an advers~ to cause serious darnage to the energy inbstmcturei~. This damage could arise through cyber infiltration of the SCADA networks, by physically tampering with the control networks, or through a combination of both means. SCADA system threats decompose into cyber and physical threats. One solution to the SCADA security problem is to design a standard for a highly secure KA.DA system that is both cyber, and physdly secure. Not all-physical threats are possible to guard again% but of those threats that are, high security SCADA provides confidence that the system will continue to operate in their presence. One of the most important problems in SCADA securi~ is the relationship between the cyber and physical vulnerabilities. Cyber intrusion increases physical Vulnerabilities, while in the dual problem physical tampering increases cyber vulnerabilit.ies. There is potential for feedback and the precise dynamics need to be understood. As a first step towards a stan~ the goal of this paper is to facilitate a discussion of the requirements analysis for a highly secure SCADA system. The fi-arnework for the discussion consists of the identification of SCADA security investment areas coupled with the tradeoffs that will force compromises in the solution. For example, computational and bandwidth requirements of a security standard could force the replacement of entire SCADA systems. The requirements for a real-time response in a cascading electric power failure could pose limitations on authentication and encryption mechanisms. The shortest path to the development of a high securi~ SC.ADA standard will be achieved by leveraging existing standards efforts and ensuring that security is being properly addressed in those standards. The Utility Communications Architecture 2.o (UC@, for real-time utili~ decision control, represents one such standard. The development of a SCADA secwiy specification is a complex task that will benefit from a systems engineering approach