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Programmable Logic Controllers (PLCs) are pivotal in Critical Infrastructures (CIs) and Industrial Control Systems (ICSs), governing processes in nuclear power plants, petrochemical factories, and water treatment systems. Despite their importance, PLCs are vulnerable to security threats, notably control logic injection attacks, aiming to sabotage physical processes. This thesis delves into PLC security, analyzing vulnerabilities in non-cryptographically and cryptographically protected PLCs, particularly Siemens S7-300 and S7-1500 models.
Siemens, an automation market leader, utilizes S7-300 PLCs in millions of applications, reflecting the broader ICS security landscape. The S7-1500 line claims resistance to cyberattacks, including control logic injections. The thesis evaluates authentication in non-cryptographically protected PLCs, introducing a stealthy control logic injection attack scenario using an S7-300 PLC and S7Comm protocol.
The second part explores integrity checks in cryptographically protected S7-1500 PLCs. Findings, encompassing disclosed vulnerabilities, lead to a severe control logic injection attack with a malicious interrupt block, conducted in an industrial setting using the S7-1500 and S7CommPlus protocol.
The final segment focuses on Profinet protocol security and an injection attack scenario. The study demonstrates adversaries manipulating critical data without prior knowledge, causing harm to physical processes. A real-world attack on a Profinet-based system with two S7-300 PLCs is executed.
The thesis concludes by proposing mitigation solutions, enhancing PLC and communication protocol security. This contribution elevates the security posture of millions of operating devices globally, advancing PLC security research.
More and more modern group oriented collaborative applications use the peer-to-peer (P2P) paradigm to be independent of expensive infrastructures as they are, for instance, provided for audio and video conferences by H.323 systems. Decentralized P2P systems better support spontaneity and mobility to set up meetings at varying locations or in ad hoc environments. This is especially advantageous for business communication over the Internet but also for other collaborative applications such as audio/video conferences. Decentralized collaborative P2P solutions require appropriate mechanisms to protect group privacy and data integrity. The broadly available security infrastructures, like virtual private networks (VPN) in the link, network, and transport layer, do not well fulfill the requirements regarding security, efficiency, and flexibility raised by a conferencing system. A dedicated security architecture in the application layer is, therefore, highly desired for protecting a P2P video conference. A centralized client/server based video conference system can be well shielded in a standard manner, whilst there exist no off-the-shelf approaches to specifying how to secure a P2P video conference up to now. This Ph.D. thesis addresses this urgent issue by presenting an effective and flexible security architecture and showing how it can be embedded into a P2P video conferencing system using the BRAVIS system as example. The cornerstone of the security architecture is the decentralized group key management. For this purpose, a new distributed key exchange protocol has been proposed. It is especially well suited for applications in real-time P2P settings for its higher efficiency than existing ones concerning the group key renewal delay. Furthermore, a novel video encryption algorithm has been developed to meet the strict real-time constraints required in a video conference. Its outstanding features include a good balance between security and efficiency, no impairment on video compression efficiency, and readily integration into the existing multimedia systems. These make it more practicable to encrypt video data than existing approaches.