On Security in Safety-Critical Process Control

This Licentiate thesis is about security in automation networks with emphasis on fieldbus communication. In the process industry, network and system security have become even more important since the introduction of Ethernetbased fieldbus protocols. As an example, a successful attack on a power plant, supporting large cities with energy, could result in a temporal but total power loss. Such attacks could be devastating for the society. The security threats are real, and motivations for attacking industrial communication systems may be political or economical. The visions of autonomous systems, which can be supervised, diagnosed and maintained from remote is not far from reality, but stress the need for security and safety measures. Wired fieldbus protocols are mature when it comes to safety and there are existing standards for safe communication. In a setup like an autonomous system security measures over safe communication has to be taken into account. The state-of-the-art in automation security is to use firewalls to restrict incoming and outgoing traffic to the networks. Firewalls can be deployed between different automation networks, i.e. server, control, and fieldbus networks, and even protect a single automation cell with a dedicated firewall. If an adversary can penetrate the perimeter defenses, no other security countermeasures exist in process automation to protect the safety-critical communication from sabotage. In this thesis we initially explore the possibilities of security attacks on the automation protocols PROFINET IO and PROFIsafe. We show that it is possible to attack safety-related communication to take control of safety-critical fieldbus nodes. We propose the concept of Security Modules in combination with PROFINET IO and PROFIsafe to achieve safe and secure real-time fieldbus communication.