Ransomware ” may be a term you haven’t heard before. This type of criminal malware, which spread around the world on PCs in 2012, encrypts some or all the files on a computer and holds them for ransom. For a hacker, a pop up message is just one more way to steal money by sending fake alerts and serious warnings that scare a user into making a payment. Ransom demands vary and can be anywhere between $30-$100. Cybercriminals have been found to earn up to $30,000 a day on scams such as these!
Source: https://thehackernews.com/2013/07/Android-Ransomware-malware-mohit-kumar-hacker.html