Ransomware is a special form of malicious soft­ware that literally “kid­naps” third-party data: attackers use ransom­ware to encrypt the (private and sensitive) data of their victims and demand a ransom for a key with which the affected parties can supposedly unlock their data once more. A prominent example on a vast scale was the WannaCry attack of May 2017: In the attack, a crypto-Trojan encrypted and locked thousands of computers world­wide.