A group of security researchers has uncovered what is believed to be the first real example of malware that is capable to reset the PIN code on a device and permanently lock the owner out of their own smartphone or tablet. This Android PIN-locking ransomware, identified as Android/Lockerpin.A, changes the infected device’s lock screen PIN code and leaves victims with a locked mobile screen, demanding for a $500 ( 450) ransom. Even paying the ransom amount won’t give you back your device access.
Source: https://thehackernews.com/2015/09/android-lock-ransomware.html