Security Analysis of Multilayer SCADA Protocols

Abstract

The layering of protocols in critical infrastructure networks – exemplified by Modbus TCP in the oil and gas sector and SS7oIP in the telecommunications sector – raises important security issues. The individual protocol stacks, e.g., Modbus and SS7, have certain vulnerabilities, and transporting these protocols using carrier protocols, e.g., TCP/IP, brings into play the vulnerabilities of the carrier protocols. Moreover, the layering produces unintended inter-protocol interactions and, possibly, new vulnerabilities. This paper describes a formal methodology for evaluating the security of multilayer SCADA protocols. The methodology, involving the analysis of peer-to-peer communications and multilayer protocol interactions, is discussed in the context of Modbus TCP, the predominant protocol used for oil and gas pipeline operations.