On the Construction of a False Digital Alibi on the Android OS

Digital evidence can determine either the conviction or acquittal of a suspect. In the latter case, such information constitutes a digital alibi. It has been recently shown how it is possible to set up a common PC in order to produce digital evidence in an automatic and systematic manner. Such traces are indistinguishable post-mortem from those left by human activity, thus being exploitable to forge a digital alibi. Modern smart phones are becoming more and more similar to PCs, due both to their computational power as well as their capacity to produce digital evidence, local or remote, which can assume a probative value. However, smart phones are still substantially different from common PCs, with OS limitations, lack of tools and so on, thus making it difficult to adopt the same techniques proposed for PCs to forge a digital alibi on a mobile device. In this paper novel techniques to create a false digital alibi on a smart phone equipped with the Android OS are presented. In particular, it is possible to simulate human interaction with a mobile device using a software automation, with the produced traces being indistinguishable post-mortem from those left by a real user. Moreover, it will be shown that advanced computer skills are not required to forge a digital alibi on an Android device, since some of the presented techniques can be easily carried out by non-savvy users. This emphasizes how the probative value of digital evidence should always be evaluated together with traditional investigation techniques.