This is an emerging form of ransomware. A hacker drops a large number of files into a hidden folder on the target's hard drive. Once they establish that the target hasn't found and hasn't deleted the files, they contact and threaten to expose the target to the authorities. The ransom is usually requested in the form of Bitcoins.
Example of a similar scam recently popped up on one of my favorite tech-sites. These scams are a little more common in Europe, where bitcoin exchange is more popular.
For reference: http://www.theregister.co.uk/2013/04...ut_ransomware/