The type of malware that disguises itself as legitimate software is known as trojan or trojan horse. Trojans trick users into installing them, believing they perform a useful function, while they actually enable unauthorized access to the user’s system. They can steal sensitive information or create openings for viruses and other malicious software. Unlike viruses and worms, trojans do not replicate themselves independently but rely on user action to spread. Awareness and caution are essential in preventing such security threats.