A dropper discovered by researchers on Google Play abuses accessibility services in a unique way to deliver Android malware.
The threat was analyzed by experts at Zscaler and Securify after finding an app on Google Play named “Earn Real Money Gift Cards.” The application hides a variant of the Android banking trojan BankBot, whose source code was leaked online in late 2016.
The developer of the app hiding BankBot also created another application present on Google Play, a game named “Bubble Shooter Wild Life.” This game actually works, but it also includes functionality that turns it into a malware downloader.
The dropper appears to be under development, but an analysis of its code, which has been protected by its creator using the Allatori Obfuscator, shows that it first requests permission to draw over other apps. It then waits 20 minutes before initiating its malicious routines, which is likely how it managed to bypass Google’s Bouncer security system.
The dropper then tricks the user into giving it accessibility permissions by displaying a fake Google Service alert. While victims believe they are enabling a “Google Service,” they are actually enabling accessibility features.
Once this step has been completed, a fake Google service update window is displayed and an APK from the device’s memory card is installed in the background. The process that takes place in the background also involves enabling the Android option that allows installation of apps from unknown sources. The user does not need to perform any other actions after accessibility permissions are granted as everything else takes place automatically in the background.
Researchers from both Zscaler and Securify believe this particular type of accessibility services abuse is unique to this piece of malware.
Securify told SecurityWeek that this dropper is sold on dark web marketplaces to cybercriminals looking to deliver Android trojans such as Exo, Mazar and BankBot.
Google has known about the malicious applications, which have a total of less than 5,000 downloads, for at least two days, but they have yet to be removed from Google Play.
Malware that abuses Android accessibility services is not uncommon, but cybercriminals keep finding new ways to exploit the feature. A study conducted last year by enterprise mobile security firm Skycure revealed that a majority of Android devices are vulnerable to attacks that trick users into enabling accessibility features via clickjacking.
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