Ransomware is a kind of malware that get  installed on your computer by mail or more likely using the browser. Ransomware encrypts part of your data. By paying a ransom you get a piece of software, which decrypts the data again. Another name of this malware is cryptoware or cryptoworm.

A big disadvantage for the criminals is the need of the contact with the victim. It is not good enough just to encrypt the data, they also need to contact the victim that the victim has the chance to pay them the ransom. In this case there is a link between the victim and the criminals which can be tracked.