  With the popularity of mobile devices, mobile applications have become an
essential part of people's lives. To provide secure mobile application download
channels for users, various modern app markets are maintained by different
companies. For example, Google maintains Google Play for Android users, while
Apple maintains App Store for iOS, iPadOS, and MacOS users. Though app markets
have come up with strict policies which impose restrictions on developers to
avoid the potential harmful applications, we still have quite limited knowledge
on the process of app vetting and the status of potential harmful apps. To fill
this gap, this paper takes the initiative to conduct a large-scale and
longitudinal study of removed apps in the iOS app store. Our analysis reveals
that although most of the removed apps are low-quality apps, a number of them
are quite popular. Furthermore, the mis-behaviors of these apps are reflected
on app metadata, which makes it possible to distinguish potential harmful apps.
