4. When your phone or tablet reboots, you should see a "Safe Mode" watermark (at the bottom of the screen). Go to your device Settings menu, tap “Apps” or “Application manager”. Touch the application you wish to uninstall (which causes the rogue ransom-demanding message to appear on your device, for example, PornDroid).
Some newer Android devices boot into Safe Mode by holding the volume up and volume down button simultaneously when restarting.
To protect your Android device from these ransomware infections, disallow third party application installation. Go to “Settings”, select “Security”, scroll down and uncheck the “Unkown sources” box.