  Supply chain security has become a growing concern in security risk analysis
of the Internet of Things (IoT) systems. Their highly connected structures have
significantly enlarged the attack surface, making it difficult to track the
source of the risk posed by malicious or compromised suppliers. This chapter
presents a system-scientific framework to study the accountability in IoT
supply chains and provides a holistic risk analysis technologically and
socio-economically. We develop stylized models and quantitative approaches to
evaluate the accountability of the suppliers. Two case studies are used to
illustrate accountability measures for scenarios with single and multiple
agents. Finally, we present the contract design and cyber insurance as economic
solutions to mitigate supply chain risks. They are incentive-compatible
mechanisms that encourage truth-telling of the supplier and facilitate reliable
accountability investigation for the buyer.
