Benjamin Andow, IBM T.J. Watson Research Center; Samin Yaseer Mahmud, Justin Whitaker, William Enck, and Bradley Reaves, North Carolina State University; Kapil Singh, IBM T.J. Watson Research Center; Serge Egelman, U.C. Berkeley; ICSI; AppCensus Inc.
Identifying privacy-sensitive data leaks by mobile applications has been a topic of great research interest for the past decade. Technically, such data flows are not “leaks” if they are disclosed in a privacy policy. To address this limitation in automated analysis, recent work has combined program analysis of applications with analysis of privacy policies to determine the flow-to-policy consistency, and hence violations thereof. However, this prior work has a fundamental weakness: it does not differentiate the entity (e.g., first-party vs. third-party) receiving the privacy-sensitive data. In this paper, we propose POLICHECK, which formalizes and implements an entity-sensitive flow-to-policy consistency model. We use POLICHECK to study 13,796 applications and their privacy policies and find that up to 42.4% of applications either incorrectly disclose or omit disclosing their privacy-sensitive data flows. Our results also demonstrate the significance of considering entities: without considering entity, prior approaches would falsely classify up to 38.4% of applications as having privacy-sensitive data flows consistent with their privacy policies. These false classifications include data flows to third-parties that are omitted (e.g., the policy states only the first-party collects the data type), incorrect (e.g., the policy states the third-party does not collect the data type), and ambiguous (e.g., the policy has conflicting statements about the data type collection). By defining a novel automated, entity-sensitive flow-to-policy consistency analysis, POLICHECK provides the highest-precision method to date to determine if applications properly disclose their privacy-sensitive behaviors.
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author = {Benjamin Andow and Samin Yaseer Mahmud and Justin Whitaker and William Enck and Bradley Reaves and Kapil Singh and Serge Egelman},
title = {Actions Speak Louder than Words: {Entity-Sensitive} Privacy Policy and Data Flow Analysis with {PoliCheck}},
booktitle = {29th USENIX Security Symposium (USENIX Security 20)},
year = {2020},
isbn = {978-1-939133-17-5},
pages = {985--1002},
url = {https://www.usenix.org/conference/usenixsecurity20/presentation/andow},
publisher = {USENIX Association},
month = aug
}