Android Installer Hijacking Vulnerability Exposes Users of Third-Party Apps to Data Theft and Malware

Palo Alto Networks today revealed details of a widespread vulnerability in Google’s Android mobile operating system that allows attackers to hijack the installation of a seemingly safe Android application -- Android Package File (APK) -- on user devices, and replace it with an app of the attacker’s choice, without user knowledge.

Exploitation of this vulnerability, which is estimated to affect about 49.5% of current Android device users, allows attackers to potentially distribute malware, compromise devices and steal user data. Palo Alto Networks today also released an application to help potentially affected Android users diagnose their devices.

Discovered by Palo Alto Networks Unit 42 threat researcher Zhi Xu, the vulnerability exploits a flaw in Android’s “PackageInstaller” system service, allowing attackers to silently gain unlimited permissions in compromised devices. During installation, Android applications list the permissions requested to perform their function, such as a messaging app requesting access to SMS messages, but not GPS location.
This vulnerability allows attackers to trick users by displaying a false, more limited set of permissions, while potentially gaining full access to the services and data on the user’s device, including personal information and passwords. While users believe they are installing a flashlight app, or a mobile game, with a well-defined and limited set of permissions, they are actually running potentially dangerous malware.

“This Android vulnerability means users who think they’re accessing legitimate applications with approved permissions may instead be exposed to data theft and malware. We urge users to take advantage of the diagnostic application provided by Palo Alto Networks to check their devices, and we thank Google, Samsung and Amazon for their cooperation and attention,” says Ryan Olson, Intelligence Director, Unit 42, Palo Alto Networks

Mitigation

The vulnerability disclosed today affects Android applications downloaded from third-party sources, and does not affect applications accessed from Google Play. Palo Alto Networks recommends the following for enterprises concerned about the risk of malware through Android devices:
• On vulnerable devices, only install software applications from Google Play; these files are downloaded into a protected space, which cannot be overwritten by the attacker.
• Deploy mobile devices with Android 4.3_r0.9 and later, but keep in mind that some Android 4.3 devices are found to be vulnerable.
• Do not provide apps with permission to access logcat. Logcat is a system log, which can be used to simplify and automate the exploit. Android 4.1 and later versions of Android by default forbid apps from accessing logcat of system and other installed apps. But an installed app could still manage to get access to other apps’ logcat on rooted mobile devices using Android 4.1 or later.
• Do not allow enterprise users to use rooted devices with enterprise networks.