Towards Industrial Intrusion Prevention Systems: A Concept and Implementation for Reactive Protection

System intrusions violate the security of a system. In order to maintain it, it is necessary to decrease the chances of intrusions occurring or by detecting them as soon as they ensue in order to respond to them in a timely manner. These responses are divided in two types: passive or reactive responses. Passive responses are limited to only notification and alerting; whereas, reactive responses influence the intrusion by undoing or diminishing its consequences. Unfortunately, some reactive responses may influence the underlying system where the intrusion has occurred. This is especially a concern in the field of Industrial Automation Systems, as these systems are critical and have a well-defined set of operational requirements that must be maintained. Hence, automatic reactive responses are often not considered or are limited to human intervention. This paper addresses this issue by introducing a concept for reactive protection that integrates the automatic execution of active responses that do not influence the operation of the underlying Industrial Automation System. This concept takes into consideration architectural and security trends, as well as security and operational policies of Industrial Automation Systems. It also proposes a set of reactive actions that can be taken in the presence of intrusions in order to counteract them or diminish their effects. The feasibility and applicability of the presented concept for Industrial Automation Systems is supported by the implementation and evaluation of a prototypical Reactive Protection System.