Google has taken steps to axe dozens of malicious apps from the official Play Store that were spotted propagating Facestealer, Joker, and Coper malware families through the virtual marketplace.
Bad actors have repeatedly found ways to sneak past security barriers put up by Google in hopes of luring unsuspecting users into downloading the fraudulent apps.
On Monday, researchers Viral Gandhi and Himanshu Sharma said in a report that “Joker is one of the most prominent malware families targeting Android devices.”
“Despite public awareness of this particular malware, it keeps finding its way into Google’s official app store by regularly modifying the malware’s trace signatures including updates to the code, execution methods, and payload-retrieving techniques.”
Joker (aka Bread) is categorised as fleeceware and designed to subscribe users to unwanted paid services or make calls to premium numbers. The fleeceware also gathers user data, such as contact lists. It was first found in the Play Store in 2017.
53 Joker downloader apps have been identified by the two cybersecurity firms. It is estimated that the applications have been downloaded over 330,000 times. These apps typically pose as photo editors, emoji keyboards, and translation apps. They thrive by asking for elevated permissions.
The researchers explained the new tactic adopted by the persistent malware to bypass detection: “Instead of waiting for apps to gain a specified volume of installs and reviews before swapping for a malware-laced version, the Joker developers have taken to hiding the malicious payload in a common asset file and package application using commercial packers.”
Security researcher Maxime Ingrao last week disclosed eight apps containing a different variant of the malware called Autolycos that racked up a total of over three million downloads prior to their removal from the app store after six months.
Pieter Arntz, Malwarebytes researcher, said “what is new about this type is that it no longer requires a WebView… Not requiring a WebView greatly reduces the chances that the user of an affected device notices something fishy is going on. Autolycos avoids WebView by executing URLs on a remote browser and then including the result in HTTP requests.”
Additionally, other apps embedding Facestealer and Coper malware have been found in the official marketplace. Facestealer enables operators to siphon Facebook credentials and auth tokens. Coper, a descendent of the Exobot malware, functions as a banking trojan that can steal a wide range of user data. The malicious malware has been found in the Vanilla Camera and Unicc QR Scanner apps.
The researchers said that Coper is “capable of intercepting and sending SMS text messages, making USSD (Unstructured Supplementary Service Data) requests to send messages, keylogging, locking/unlocking the device screen, performing overly attacks, preventing uninstalls and generally allowing attackers to take control and execute commands on infected device via remote connection with a C2 server.”
Evolving tactics used by threat actors to stay under the radar help get them onto the official app store.
Users have been warned to refrain from granting unnecessary permissions to apps and to verify their legitimacy by checking reviews, developer information and reading their privacy policies.