The correct answer is 'Ransomware' as it is typically defined as malicious software that encrypts the victim's files and demands payment for the decryption key. 'Trojans' are a form of malware that appears legitimate but can take control of your computer. 'Worms' are malware that replicates itself to spread to other computers, often causing harm by consuming bandwidth or corrupting data. 'Logic bombs' are a string of code that will set off a malicious function when specified conditions are met. In this scenario, since the malware encrypts data and requires a ransom, the description aligns with ransomware.