"You just can't know about everything" - Privacy Perceptions of Smart Home Visitors.

IoT devices can harvest personal information of any person in their surroundings and this includes data from visitors. Visitors often cannot protect their privacy in a foreign smart environment. This might be rooted in a poor awareness of privacy violations by IoT devices, a lack of knowledge, or a lack of coping strategies. Thus, visitors are typically unaware of being tracked by IoT devices or lack means to influence which data is collected about them. We interviewed 21 young adults to investigate which knowledge visitors of smart environments need and wish to be able and protect their privacy. We found that visitors consider their relation to the IoT device owner and familiarity with the environment and IoT devices when making decisions about data sharing that affect their privacy. Overall, the visitors of smart environments demonstrated similar privacy preferences like the owners of IoT devices but lacked means to judge consequences of data collection and means to express their privacy preferences. Based on our results, we discuss prerequisites for enabling visitor privacy in smart environments, demonstrate gaps in existing solutions and provide several methods to improve the awareness of smart environment visitors.