How risky are real users' IFTTT applets?

Smart-home devices are becoming increasingly ubiquitous and interconnected with other devices and services, such as phones, fitness trackers, cars, and social media accounts. Built-in connections between these services are still emerging, but end-user-programming tools such as If-This-Then-That (IFTTT) have existed for almost a decade, allowing users to create rules (called applets in IFTTT) that dictate interactions between devices and services. Previous work found potential secrecy or integrity violations in many applets, but did so without examining how individual users interact with the service. In this work, we study the risks of real-world use of IFTTT by collecting and analyzing 732 applets installed by 28 participants and participants' responses to several survey questions. We found that significantly fewer applets than previously thought pose realistic secrecy or integrity risks to the users who install them. Consistent with this finding, participants were generally not concerned about potential harms, even when these were explained to them. However, examining participants' applets led us to identify several new types of privacy risks, which challenge some assumptions inherent in previous analyses that focus on secrecy and integrity risks. For example, we found that many applets involve monitoring incidental users: family, friends, and neighbors who may interact with someone else's smart-home devices, possibly without realizing it. We discuss what our findings imply for automatically identifying potentially harmful applets.