This type of Trojan modifies data on the victim computer so that the victim can no longer use the data, or it prevents the computer from running correctly. Once the data has been “taken hostage” (blocked or encrypted), the user will receive a ransom demand.
The ransom demand tells the victim to send the malicious user money; on receipt of this, the cyber criminal will send a program to the victim to restore the data or restore the computer’s performance.