  The Internet of things (IoT) will make it possible to interconnect and
simultaneously control distributed electrical loads. Various technical and
regulatory concerns have been raised that IoT-operated loads are being deployed
without appropriately considering and systematically addressing potential
cyber-security challenges. Hence, one can envision a hypothetical scenario when
an ensemble of IoT-controlled loads can be hacked with malicious intentions of
compromising operations of the electrical grid. Under this scenario, the
attacker would use geographically distributed IoT-controlled loads to alternate
their net power injections into the electrical grid in such a way that may
disrupt normal grid operations.
  This paper presents a modeling framework to analyze grid impacts of
distributed cyber-attacks on IoT-controlled loads. This framework is used to
demonstrate how a hypothetical distributed cyber-attack propagates from the
distribution electrical grid, where IoT-controlled loads are expected to be
installed, to the transmission electrical grid. The techno-economic
interactions between the distribution and transmission electrical grids are
accounted for by means of bilevel optimization. The case study is carried out
on the modified versions of the 3-area IEEE Reliability Test System (RTS) and
the IEEE 13-bus distribution feeder. Our numerical results demonstrate that the
severity of such attacks depends on the penetration level of IoT-controlled
loads and the strategy of the attacker.
