  Security researchers have recently discovered significant security and safety
issues related to home automation and developed approaches to address them.
Such approaches often face design and evaluation challenges which arise from
their restricted perspective of home automation that is bounded by the IoT apps
they analyze. The challenges of past work can be overcome by relying on a
deeper understanding of realistic home automation usage. More specifically, the
availability of natural home automation scenarios, i.e., sequences of home
automation events that may realistically occur in an end-user's home, could
help security researchers design better security/safety systems. This paper
presents Helion, a framework for building a natural perspective of home
automation. Helion identifies the regularities in user-driven home automation,
i.e., from user-driven routines that are increasingly being created by users
through intuitive platform UIs. Our intuition for designing Helion is that
smart home event sequences created by users exhibit an inherent set of semantic
patterns, or naturalness that can be modeled and used to generate valid and
useful scenarios. To evaluate our approach, we first empirically demonstrate
that this naturalness hypothesis holds, with a corpus of 30,518 home automation
events, constructed from 273 routines collected from 40 users. We then
demonstrate that the scenarios generated by Helion are reasonable and valid
from an end-user perspective, through an evaluation with 16 external
evaluators. We further show the usefulness of Helion's scenarios by generating
17 home security/safety policies with significantly less effort than existing
approaches. We conclude by discussing key takeaways and future research
challenges enabled by Helion's natural perspective of home automation.
