  The General Data Protection Regulation (GDPR) aims to ensure that all
personal data processing activities are fair and transparent for the European
Union (EU) citizens, regardless of whether these are carried out within the EU
or anywhere else. To this end, it sets strict requirements to transfer personal
data outside the EU. However, checking these requirements is a daunting task
for supervisory authorities, particularly in the mobile app domain due to the
huge number of apps available and their dynamic nature. In this paper, we
propose a fully automated method to assess the compliance of mobile apps with
the GDPR requirements for cross-border personal data transfers. We have applied
the method to the top-free 10,080 apps from the Google Play Store. The results
reveal that there is still a very significant gap between what app providers
and third-party recipients do in practice and what is intended by the GDPR. A
substantial 56% of analysed apps are potentially non-compliant with the GDPR
cross-border transfer requirements.
