Evil genius, but genius none the less,' an IT professional commented in an online tech forum. Open that file and bad things start to happen, although it may take several days for the ransom demand to appear on your screen after the machine is infected. One small business reports being compromised after clicking on an email attachment that was designed to look like a shipping invoice from the U.S. This sophisticated malware is delivered the old-fashioned way: an executable file hidden inside an attachment that looks like an ordinary ZIP file or PDF. One victim described his anguish in an online post: 'The virus cleverly targeted … all of our family photos, including all photos of my children growing up over the last 8 years. To instill a sense of urgency, a digital clock on the screen counts down from 72 hours so you can see how much time is left before that unique decryption key is destroyed. The typical extortion payment is $300 or 300 euros paid by Green Dot MoneyPak, or for the more tech-savvy, two bitcoins, currently worth about $400. ( Read more: New security threat: Cash register skimmers)

And as the message from the extortionists says, 'After that, nobody and never will be able to restore files. Unless you pay the ransom within three days, that key will be destroyed. There's only one decryption key, and the bad guys have that on their server.

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