Automatic deployment of specification-based intrusion detection in the BACnet Protocol

Specification-based intrusion detection (SB-ID) is a suitable approach to monitor Building Automation Systems (BASs) because the correct and non-compromised functioning of the system is well understood. Its main drawback is that the creation of specifications often require human intervention. We present the first fully automated approach to deploy SB-ID at network level. We do so in the domain of BASs, specifically, the BACnet protocol (ISO 16484-5). In this protocol, properly certified devices are demanded to have technical documentation stating their capabilities. We leverage on those documents to create specifications that represent the expected behavior of each device in the network. Automated specification extraction is crucial to effectively apply SB-ID in volatile environments such as BACnet networks, where new devices are often added, removed, or replaced. In our experiments, the proposed algorithm creates specifications with both precision and recall above 99.5%. Finally, we evaluate the capabilities of our detection approach using two months (80GB) of BACnet traffic from a real BAS. Additionally, we use synthetic traffic to demonstrate attack detection in a controlled environment. We show that our approach not only contributes to the practical feasibility of SB-ID in BASs, but also detects stealthy and dangerous attacks.