External Verification of SCADA System Embedded Controller Firmware

摘要

Critical infrastructures such as oil and gas pipelines, the electric power grid, and railways, rely on the proper operation of supervisory control and data acquisition (SCADA) systems. Current SCADA systems, however, do not have sufficient tailored electronic security solutions. Solutions available are developed primarily for information technology (IT) systems. Indeed, the toolkit for SCADA incident prevention and response is unavailing as the operating parameters associated with SCADA systems are different from IT systems. The unique environment necessitates tailored solutions. Consider the programmable logic controllers (PLCs) that directly connect to end physical systems for control and monitoring of operating parameters -- the compromise of a PLC could result in devastating physical consequences. Yet PLCs remain particularly vulnerable due to a lack of firmware auditing capabilities. This research presents a tool we developed specifically for the SCADA environment to verify PLC firmware. The tool does not require any modifications to the SCADA system and can be implemented on a variety of systems and platforms. The tool captures serial data during firmware uploads and then verifies them against a known good firmware baseline. Attempts to inject modified and/or malicious firmware are identified by the tool. Additionally, the tool can replay and analyze captured data by emulating a PLC during firmware upload. The emulation capability enables verification of the firmware upload from an interface computer without requiring modifications to or interactions with the operational SCADA system. The ability to isolate the tool from production systems and verify the validity of firmware makes the tool a viable application for SCADA incident response teams and security engineers.