Grades are assigned using a privacy model that we built. This privacy model measures the gap between people's expectations of an app's behavior and the app's actual behavior. For example, according to studies we have conducted, most people don't expect games like Cut the Rope to use location data, but many of them actually do. This kind of surprise is represented in our privacy model as a penalty to an app’s overall privacy grade. In contrast, most people do expect apps like Google Maps to use location data. This lack of surprise is represented in our privacy model as a small or no penalty.
The main work behind PrivacyGrade was done by Jialiu Lin, Shahriyar Amini, Song Luan, Kevin Ku, Mike Villena, Bharadwaj Ramachandran, and Richmond Wong. Professors Janne Lindqvist, Norman Sadeh, and Joy Zhang also helped with some of the ideas in PrivacyGrade.
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