Smartphones, the devices we carry everywhere with us, are being heavily
tracked and have undoubtedly become a major threat to our privacy. As "tracking
the trackers" has become a necessity, various static and dynamic analysis tools
have been developed in the past. However, today, we still lack suitable tools
to detect, measure and compare the ongoing tracking across mobile OSs. To this
end, we propose MobileAppScrutinator, based on a simple yet efficient dynamic
analysis approach, that works on both Android and iOS (the two most popular OSs
today). To demonstrate the current trend in tracking, we select 140 most
representative Apps available on both Android and iOS AppStores and test them
with MobileAppScrutinator. In fact, choosing the same set of apps on both
Android and iOS also enables us to compare the ongoing tracking on these two
OSs. Finally, we also discuss the effectiveness of privacy safeguards available
on Android and iOS. We show that neither Android nor iOS privacy safeguards in
their present state are completely satisfying