Casing the Vault: Security Analysis of Vault Applications.

Vault applications are a class of mobile apps used to store and hide users' sensitive files (e.g., photos, documents, and even another app) on the phone. In this paper, we perform an empirical analysis of popular vault apps under the scenarios of unjust search and filtration of civilians by authorities (e.g., during civil unrest). By limiting the technical capability of adversaries, we explore the feasibility of inferring the presence of vault apps and uncovering the hidden files without employing sophisticated forensics analysis. Our analysis of 20 popular vault apps shows that most of them do not adequately implement/configure their disguises, which can reveal their existence without technical analysis. In addition, adversaries with rudimentary-level knowledge of the Android system can already uncover the files stored in most of the vault apps. Our results indicate the need for more secure designs for vault apps.