  Securing the supply chain of information and communications technology (ICT)
has recently emerged as a critical concern for national security and integrity.
With the proliferation of Internet of Things (IoT) devices and their increasing
role in controlling real world infrastructure, there is a need to analyze risks
in networked systems beyond established security analyses. Existing methods in
literature typically leverage attack and fault trees to analyze malicious
activity and its impact. In this paper, we develop RIoTS, a security risk
assessment framework borrowing from system reliability theory to incorporate
the supply chain. We also analyze the impact of grouping within suppliers that
may pose hidden risks to the systems from malicious supply chain actors. The
results show that the proposed analysis is able to reveal hidden threats posed
to the IoT ecosystem from potential supplier collusion.
