MockDroid: trading privacy for application functionality on smartphones

Authors:    Alastair R. Beresford,  Computer Laboratory, University of Cambridge

Andrew Rice ,                  Computer Laboratory, University of Cambridge

Nicholas Skehin,             Computer Laboratory, University of Cambridge

Ripduman Sohan,           Computer Laboratory,  University of Cambridge

This paper describes a special Android system that can be used to protect smart-phone users’ privacy. Nowadays, there are thousands of third party applications used by smart-phone users. Those programs can be malicious and used to compromise privacy without being detected. For example, a game that is called Paper Toss asks the user to grant GPS location permission. Playing this game does not need GSP location at all. The reason why it asks for GPS location permission is that it can display advertisements given the user’s current location. This examples shows that many applications expose a user’s private information without his or her consent.  This paper introduces a “Mock” Android system that is designed to protect privacy without deathly affecting the functionality of an application. In other words, MockDroid system shows that we can trade privacy for application functionality.

The mechanism of “MockDroid” is to fake the data that is used by a program. When a user tries to install an application on his or her Android phone, the program will ask for access permissions, such as Internet permission, GPS location permission, etc. The user has to grant the permissions in order to install the program; otherwise, the application will not be installed. At that time, the user can grant those permissions to the program and it will be installed. However, he or she can provide a “fixed” and “spurious” data to the permission-granted APIs by using MockDroid. In this way, the user’s privacy is protected. For example, the Paper Toss game sends its user’s GPS location to a remote server periodically. The user can provide a fixed location such as latitude: 30.8849748 and longitude: 43.874748433 when the application tries to send the GPS location data back to the server. As a result, the user’s real GPS location is protected from revealing to the remote server.

There is a trade-off between privacy and application functionality.  Some applications need the user’s GPS location to provide a better service. If the user’s provide a “spurious” GPS location, then he is less likely to get a pleasant result or service. For example, an application that displays the nearby gas stations cannot provide a good service without knowing the user’s current location. “Mocking” the GPS location is detriment to this application’s performance. This suggests that trading privacy for application functionality can bring users frustrating results.

In conclusion, the “MockDroid” system plays an important role in protecting privacy. This paper shows that there is a need to protect smart-phone users’ privacy, since there are many third-party applications attempts to compromise privacy. However, protecting privacy is not completely free. It may cause a program to function incorrectly. Therefore, it is important for future researchers to consider how to protect privacy without losing application functionality.