New Sophisticated Android Ransomware that Doesn’t Encrypt Files but Blocks Access to Devices

Microsoft detected new Android ransomware with new attack techniques and behavior that indicates the evolution of mobile ransomware.

As we aware ransomware uses to encrypt files, but this new ransomware doesn’t encrypt files, instead, it blocks access to devices by displaying a warning screen.

Sophisticated new Android malware

Android ransomware uses a special permission “SYSTEM_ALERT_WINDOW” to display the ransom note on top of other application and it can be dismissed by clicking any button.

This permission is to notify the user’s system alerts or errors, but the Android threat misused it to gain access over the display.

The new Android ransomware variant uses “call” notification Android to gain immediate user attention and uses the onUserLeaveHint() callback function whenever the malware screen is pushed to the background, causing the in-call Activity to be automatically brought to the foreground.

“This ransomware is the latest variant of a malware family that has undergone several stages of evolution. We expect it to churn out new variants with even more sophisticated techniques,” reads Microsoft analysis.

The malware is highly obfuscated, it has no code corresponding to the services declared in the manifest file: Main Activity, Broadcast Receivers, and Background.

According to Microsoft analysis, the code is heavily obfuscated and made unreadable through name mangling and uses an interesting decryption routine, in that decryption function does not correspond to the decrypted value, they correspond to junk code to simply hinder analysis.

“This new mobile ransomware variant is an important discovery because the malware exhibits behaviors that have not been seen before and could open doors for other malware to follow,”

“The discovery reinforces the need for comprehensive defense powered by broad visibility into attack surfaces as well as domain experts who track the threat landscape and uncover notable threats that might be hiding amidst massive threat data and signals.”

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