The WannaCry bug encrypts users’ files and demands a Bitcoin ransom in return for the unlock key. Only those that have disabled security updates are vulnerable to it. Rhett Jones looked into the earnings of the perpetrators:

• One expert used publicly available Bitcoin data to estimate that WannaCry’s creators had made just $26,000.
• There is evidence that some users may even have negotiated down the original asking ransom price of $300.
• The bug threatens to double prices if users don’t immediately pay the ransom so it’s possible earnings will jump.
• Analysis done in 2012 indicated that approximately 3% of people pay up when hit with ransomware attacks.

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