The email from the bank looked innocent enough. It was from paymentsadmin@lloydsplc.co.uk, and Sarah Flanders, a 35-year-old charity worker from north London, didn't think twice about opening it. But the email contained software that immediately began encrypting every file on her computer ? from precious family photos to private correspondence and work documents. In just a short time all her files were blocked, and then a frightening message flashed up on her screen: "Your personal files have been encrypted and you have 95 hours to pay us $300."

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