A Trojan virus is a type of malicious software that disguises itself as a legitimate program to trick users into downloading and installing it. Unlike other viruses, Trojans do not replicate themselves; instead, they rely on users to execute them. Once activated, they can steal personal information, create backdoors for other malware, or damage files. Trojans can be delivered through various means, such as email attachments, infected software downloads, or compromised websites. To protect against Trojan viruses, users should maintain updated antivirus software, avoid suspicious downloads, and be cautious with email links and attachments.