SUPOR: Precise and Scalable Sensitive User Input Detection for Android Apps

While smartphones and mobile apps have been an essential part of our lives, privacy is a serious concern. Previous mobile privacy related research efforts have largely focused on predefined known sources managed by smartphones. Sensitive user inputs through UI (User Interface), another information source that may contain a lot of sensitive information, have been mostly neglected. 

In this paper, we examine the possibility of scalably detecting sensitive user inputs from mobile apps. In particular, we design and implement SUPOR, a novel static analysis tool that automatically examines the UIs to identify sensitive user inputs containing critical user data, such as user credentials, finance, and medical data. SUPOR enables existing privacy analysis approaches to be applied on sensitive user inputs as well. To demonstrate the usefulness of SUPOR, we build a system that detects privacy disclosures of sensitive user inputs by combining SUPOR with off-the-shelf static taint analysis We apply the system to 16,000 popular Android apps, and conduct a measurement study on the privacy disclosures. SUPOR achieves an average precision of 97.3% and an average recall of 97.3% for sensitive user input identification. SUPOR finds 355 apps with privacy disclosures and the false positive rate is 8.7%. We discover interesting cases related to national ID, username/password, credit card and health information.