Security researchers have found a malicious application on Google Play that had over 500,000 downloads and was designed to gain complete control over Android devices.
The application masqueraded as a guide for the popular Pokémon Go game and used multiple layers of obfuscation to bypass Google Play's malware detection mechanisms, researchers from Kaspersky Lab said in a blog post.
The app contains a malicious module that doesn't execute immediately. Instead, the app waits for another application to be installed or uninstalled in order to determine if it's running on a real device or in an emulated environment, like the ones used to detect malware.
Once the app determines that it runs on a real device, it waits a further two hours before executing the malicious module, which then connects to a remote server and sends data about the device. The server can instruct the module to download exploits for local privilege escalation vulnerabilities that were discovered in Android between 2012 and 2015.
These are known as root exploits because they grant access to the highest privileged account on Android -- the root account. In other words, successful exploitation will lead to a full compromise of the device.
Google has released patches for all of these vulnerabilities, but because of the fragmentation of the Android ecosystem, there are likely many devices out there that haven't received all the updates.
This doesn't mean that the 500,000 downloads represent the number of compromised devices. Android has local protection features like Verify Apps and SafetyNet that are specifically designed to detect and block known root exploits.
Kaspersky identified over 6,000 successful infections, primarily in Russia, India and Indonesia. "However, since the app is oriented towards English-speaking users, people in such geographies, and more, are also likely to have been hit," the Kaspersky researchers said.
The malicious “Guide for Pokémon Go” app was not the only app in the Google Play store that contained this Trojan module. Kaspersky found other such apps that were in the store at different times since December 2015. Most of the older apps had around 10,000 downloads, but one called "Digital Clock" had more than 100,000 downloads.
Google has done a pretty good job at keeping malware out of its official app store over the past few years, but as this incident shows, malicious applications can still slip through from time to time.