Ransomware is a type of malware that will lock you out of your files, device, or other resources, and demand a payment to regain access. Even if you choose to pay up, most often the payment will not result in gaining back access, and your files are permanently lost.
The threat posed by Ransomware is serious, and ongoing. I last updated this article in September 2015, not long after Cryptolocker became the first widely reported Ransomware threat with thousands of infected computers and resulting in the loss of millions of dollars of data and production. The problem has only increased in frequency and severity with a range of new variants attacking customers across PC and other platforms.