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APEFS - An Infrastructure for Permission-based filtering of Android Apps

APEFS-Logo At the institute we develope an app that allows users to protect the data on their smartphones from sniffing apps. Those dangerous apps peek silently data from the phones or use secretly paid services like phone calls or send SMS that only comes to notice to the user on the next phone bill.

Our app "APEFS" (Android PErmission Filter System) is able to filter apps that are interesting for the user by search in charts and searches for suspicious patterns and so allows controlled installation of apps. To do so the user can use filter options, like Internetaccess or Paid services, offered by APEFS that fit to his view of security issues. APEFS then discards apps that questionable from the view of the user.

appsiegel APEFS relieves the user from reading the sometimes complex and incomprehensible permissions list and protects against unpleasant surprises. A positive side effect is the time savings.

APEFS can be adjusted to the specific needs of the user, so that he can set the filters fitting to the searches.

APEFS you can of course also be applied to the already installed apps and so find possible "black sheep". In addition APEFS provides the ability to probe the developers by letting the users send questions about the permissions of the apps.


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The technology behind APEFS

APEFS provides charts and searches based on data from Google Play. This works by simply forwarding the requests of the users to the Google Play website.

Then the web pages that are returned as the result will be searched for the name and package IDs of apps. Based on the package IDs APEFS can now request the detail sites. On these pages APEFS then finds the permissions that the app requests and saves them to the app.

Finally APEFS filters those apps with not fitting permissions. When the user wants to install an app this is done via the Google Play app. Here the user can also view the screenshots and comments of the app.

What APEFS can and can not do

APEFS is based on the permissions of the apps. So it can filter over the permissions. However APEFS can no see what the apps really do with the permissions. So just because an app has the permission to make phone calls, it doesn't means that the app is calling cost numbers. Neither has an app that can read the contacts and has full internet access to send the contacts to the internet.

The suspicious apps from the view of the user must not necessarily behave suspiciously. This problem is in the focus of our future research. We want to analyse what the apps really do. Therefore we use the so called information flow analysis of the apps. This analysis provides the possible flows of information in the apps. So in the context of the example, if the contacts are really send to the internet.

A prototypical implementation of this idea was created as part of a diploma thesis.


APEFS in the Media