Joker Trojan-Infected Android Apps Reappear on Google Play Store

Android OS Mobile Networks and Telephones
Advisory ID:
May 10, 2022


The Joker trojan malware, which targets Android devices, first showed up in 2017 and has resurfaced intermittently ever since. In April 2021, it was embedded in an App that was downloaded over seven hundred thousand (700,000) times before discovery and subsequent removal from the Google Play Store. Its latest emergence has so far triggered the removal of three (3) apps from the Play Store.

Description & Consequence

Bad actors download legitimate apps from the Play Store, modify them by embedding the trojan malware and then uploading the app back to the Play Store with a new name. The malicious payload is only activated once the apps goes live on the Play Store -- which enables the apps to scale through Google’s strict evaluation process. Once installed, these apps request for permissions that once granted, enable the apps to have access to critical functions such as text messages and notifications.

A compromised device will subscribe unwitting users to premium services, billing them for services that do not exist. A device like this can also be used to commit SMS fraud while the owner is unaware. It can click on online ads automatically and even use SMS OTPs to secretly approve payments. Without checking bank statements, the user will be unaware that he or she has subscribed to an online service. Other actions, such as stealing text messages, contacts, and other device data, are also possible. 


  1. Users should avoid downloading unnecessary apps or installing apps from unofficial sources.
  2. Apps installed from the Google Play Store should be heavily scrutinized by reading reviews, assessing the developers, perusing the terms of use and only granting the necessary permissions.
  3. Unauthorized transactions should also be checked against any installed app.
  4. Apps not in use should be deleted and users should ensure that a device is always patched and updated to the latest software.



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