Imagine a thief walks into your home and rummages through your personal belongings. But instead of stealing them, he locks all your valuables into a safe and forces you to pay a ransom for the key to unlock the safe. What choice do you have?

Substitute your digital space for your home and encryption for the safe, and you have what’s known as ransomware. Ransomware is a type of virus or malware. After the initial infection, your files are encrypted and a note appears demanding payment–usually in the form of cryptocurrency such as bitcoin because transactions can’t be stopped or reversed. Once your files are encrypted, you can’t access them until you pay the ransom.

The roots of ransomware can be traced back to 1989. The virus, known as PS Cyborg, was spread through diskettes given to attendees of a World Health Organization International AIDS conference. Victims of PS Cyborg were to mail $189 to a P.O. box in Panama to restore access to their data.

Historically, ransomware targeted individual personal computer users. Today, the big money is in attacking businesses. Most of these infections go unreported because companies don’t want to expose themselves to further attacks or reputational damage. Read On: