Behind the rise of ransomware lies the rise of Bitcoin, the virtual currency of choice for hacker blackmailers who steal huge amounts of sensitive data. The recent ransomware attack has renewed a long-running debate about the dangers of digital currency. "WannaCry" - the ransomware, asked users to pay ransom in bitcoins. The ransom note indicates the payment amount will be doubled after three days. If payment is not made after seven days, the encrypted files will be deleted. Security experts warn there is no guarantee that access will be granted after payment.