Symantec Security Response – Android ransomware requires victim to say unlock code
Latest Android.Lockdroid.E variant uses speech recognition instead of typing for unlock code input.
Targets Chinese language Android users
Being a good listener is normally considered an admirable quality in a person; however, it isn’t a quality you
necessarily want to find in a piece of malware. The latest variant of the Android ransomware threatAndroid.Lockdroid.E is a great listener. In fact, if you say the right things it might even give you back access to your phone. The threat
uses speech recognition APIs and requires its victims to speak an unlock code instead of the traditional method of
typing it in.
Once Android.Lockdroid.E infects a device it locks the user out using a SYSTEM type window and then displays a ransom
note. The ransom note is written in Chinese and gives instructions on how to unlock the device. The note provides aQQ instant messaging ID to contact in order to receive further instructions on how to pay the ransom and receive an unlock code. Since the
user’s device is locked, another device must be used to contact the cybercriminals behind the threat.
Figure 1. Lock screen with instructions
The note also instructs the victim to press a button, which starts the speech recognition functionality.
The malware uses third-party speech recognition APIs and compares the spoken words heuristically with the expected
passcode. If the input matches up, the malware removes the lockscreen.
The malware stores the lockscreen image and the relevant passcode in one of its Assets files in encoded form with
additional padding. This latest technique of using speech recognition is rather inefficient as the victim must still use
another device to contact the criminals.
It’s clear that the malware authors are continually experimenting with new methods to achieve their goal of extorting
money from their victims. We can be certain this isn’t the last trick we’ll see from this threat family.
Mitigation
Symantec recommends users follow these best practices to stay protected from mobile threats:
• Keep your software up to date
• Refrain from downloading apps from unfamiliar sites and only install apps from trusted sources
• Pay close attention to the permissions requested by apps
• Install a suitable mobile security app to protect your device and data
Make frequent backups of important data
Protection
Symantec and Norton products detect the threat discussed in this blog asAndroid.Lockdroid.E.