Which type of malware is specifically designed to spread from one infected system to another?

The correct answer is a worm. Worms are a specific type of malware that are engineered to replicate themselves and spread independently across networks, often without the need for user interaction. Unlike other malware types, such as ransomware and Trojans, which typically rely on user actions to propagate, worms can self-replicate and move across systems and networks, exploiting vulnerabilities or using social engineering techniques.

This autonomous spreading capability is what distinguishes worms from other types of malware. For instance, ransomware encrypts files on an infected system and demands payment for decryption, while Trojans masquerade as legitimate software to deceive users into installing them. Adware, on the other hand, displays unwanted advertisements, affecting user experience but not transferring itself to other systems like a worm would. Therefore, the nature of a worm is fundamentally about its ability to propagate and infect multiple machines independently, making it the correct answer to this question.