Which among the following is a malicious software ?

A Trojan Horse is a type of malicious software (malware) that disguises itself as legitimate or benign software to deceive users into installing it. Unlike viruses or worms, Trojans do not self-replicate but rely on social engineering to infiltrate systems. Once active, they can perform various malicious actions such as stealing sensitive data, monitoring keystrokes, or creating backdoors for unauthorized remote access. In contrast, hacking and password cracking are activities or techniques used by cybercriminals to gain unauthorized access, rather than being software types themselves. A firewall is a network security tool designed to act as a barrier that monitors and blocks unauthorized traffic, serving as a defense mechanism against malware like Trojans. Therefore, among the given options, only the Trojan Horse is classified as malicious software.