Launch of denial of service attacks on the modbus/TCP protocol and development of its protection mechanisms

Abstract

Modbus is considered the defacto standard of industrial control systems as obvious from the fact that most vendors in the automation industry support Modbus protocol. Despite its wide popularity, Modbus is not secure because the time period in which it was introduced security was not considered to be a concern for closed isolated Industrial Control Systems (ICS) systems, therefore, in today’s era of internet, Modbus protocol cannot withstand malicious cyber attacks that the normal IT network is exposed to. Among the various attacks launched on ICS, the Denial of Service (DoS) attack is of prime importance as it has a fatal impact on the control systems’ stability and operation specially where hard real-time communication is essential. In this paper, we perform an extensive research on the documented and reported vulnerabilities in the Modbus protocol, and also review various efforts on how to exploit those vulnerabilities. After the thorough and exhaustive research, we have designed a virtual testbed that simulates the real world industrial control systems to conduct research on exploitation of the found vulnerabilities. The testbed is employed to successfully conduct two Denial of service attack scenarios on the software simulation of a programmable logic controller. The results of the launched attacks are evaluated in an attempt to perform attack-impact analysis and their findings are discussed in this paper. Lastly, a few prevention techniques are discussed that enlist how to avoid and protect systems against these attacks.