Google recently removed 29 applications from Google Play after learning that they were actually containing code to steal users’ banking information.
The applications, found in the official app store from August until early October 2018, were masquerading as utility programs, including device boosters, cleaners and battery managers, as well as horoscope-themed apps.
These programs, ESET security researchers reveal, were sophisticated mobile banking Trojans packing complex functionality and highly focused on staying hidden. This sets them apart from the malicious apps that impersonate legitimate financial institutions and display bogus login screens.
The Trojans could dynamically target any app on the victim’s device, courtesy of tailored phishing forms. The malware operators could control them remotely to intercept and redirect text messages to bypass SMS-based two-factor authentication, intercept call logs, and download and install other apps.
Although uploaded to Google Play under different developer names, these apps presented code similarities and shared the command and control (C&C) server, which led the researchers to the conclusion they were the work of a single attacker or group.
Once installed and launched, the apps would usually display an error message, claiming incompatibility with the victim’s device and informing the user they were removed. Instead, they would only hide from the user and covertly engage in nefarious operations. Some of the apps, however, did offer the promised functionality — such as displaying horoscopes.
The malicious payload carried by the programs was encrypted and hidden in each app’s assets. When executed, the payload launches a dropper that checks for the presence of an emulator or a sandbox and only then proceeds to decrypting and dropping a loader and the actual banking malware.
The final payload was designed to impersonate banking apps installed on the victim’s device, intercept and send SMS messages, and download and install additional applications, based on the operator’s instructions.
The threat can “dynamically impersonate any app installed on a compromised device,” ESET reveals. For that, the malware obtains the HTML code of the installed apps and leverages that code to overlay bogus forms when legitimate apps are launched.
ESET says they discovered 29 such malicious apps, all of which have been removed from the official Android store. However, these programs did gather around 30,000 downloads before being removed.
“Fortunately, these particular banking Trojans do not employ advanced tricks to ensure their persistence on affected devices. Therefore, if you suspect you have installed any of these apps, you can simply uninstall them under Settings > (General) > Application manager/Apps,” ESET says.