An introduction to "ransomware"

Excerpts from an article at Wired:

Ransomware is malware that locks your keyboard or computer to prevent you from accessing your data until you pay a ransom, usually demanded in Bitcoin. The digital extortion racket is not new—it’s been around since about 2005, but attackers have greatly improved on the scheme with the development of ransom cryptware, which encrypts your files using a private key that only the attacker possesses, instead of simply locking your keyboard or computer. And these days ransomware doesn’t just affect desktop machines or laptops; it also targets mobile phones...
Symantec has estimated, conservatively, that at least $5 million is extorted from ransomware victims each year. But forking over funds to pay the ransom doesn’t guarantee attackers will be true to their word and victims will be able to access their data again. In many cases, Symantec notes, this doesn’t occur....
One ransomware attack known as Reveton that is directed at US victims produces a pop-up message saying your machine has been involved in child porn activity or some other crime and has been locked by the FBI or Justice Department. Unless you pay a fine—in Bitcoin, of course, and sent to an address the attackers control—the government won’t restore access to your system...
CryptoWall can not only encrypt files on the victim’s computer but also any external or shared drives that connect to the computer. And the shakedown demand can range anywhere from $200 to $5,000...
TorrentLocker harvests email addresses from a victim’s mail client to spam itself to other victims. Fox-IT calculated at one point that TorrentLocker had amassed some 2.6 million email addresses in this manner.
Protecting against ransomware can be difficult since attackers actively alter their programs to defeat anti-virus detection. However, antivirus is still one of the best methods to protect yourself against known ransomware in the wild. It might not be possible to completely eliminate your risk of becoming a victim of ransomware, but you can lessen the pain of being a victim by doing regular backups of your data and storing it on a device that isn’t online.

The TL;DR seems to be in the last sentence - it may be cheaper to throw out and replace your computer than to pay the ransom.