Hacker attack that makes you grind your teeth

A dental practice was hit last year by a strain of malicious software that sought out X-ray images and encrypted them on the clinic's computer system. Hackers in Eastern Europe then demanded $500 (Rs 30,223) in Bitcoins to unlock the files, according to Jeff Horne, who investigated the breach for Accuvant, a Denver-based security firm.

The ransom amount increased by $500 each day, but it wasn't paid. While ransomware has been around for years, it has typically taken the form of fake antivirus alerts. Criminals demand payment to clean the malware (their own, of course) from the victims' computers.

Now, hackers are using programs such as CryptoLocker and CryptoWall to search out valuable files, often images, on victims' machines and encrypt them, rendering them useless until a fee is paid. This type of cyber-extortion comes as more of the health-care industry goes digital with their patient records.

Last year, medical practices in Illinois and Australia were infiltrated by hackers who encrypted patients' files and held them for ransom. Security experts expect to see these kinds of incidents becoming more common. Symantec, the biggest maker of security software, detected five times more of it in 2013 compared with 2012.