What is a Trojan in the context of computer security?

In the context of computer security, a Trojan refers to a program that appears to be legitimate and benign but actually performs malicious or unintended functions once executed. This type of malware is named after the famous Trojan Horse from Greek mythology, which was used to deceive the Trojans into letting a hidden army into their city. Similarly, a Trojan often disguises itself within seemingly harmless files or applications to trick users into installing it.

Once installed, a Trojan can carry out a variety of harmful activities, such as stealing personal information, creating backdoors for unauthorized access, or downloading additional malware. The key characteristic of a Trojan is its ability to mislead the user about its true purpose, making it different from other forms of malware that may be more overt in their harmful intentions.

In contrast, self-replicating malware, such as viruses and worms, duplicately spread across systems without user intervention. Software that spreads via email often refers to specific types of malware, like worms that leverage email attachments for propagation. A rootkit is a specific type of malware designed to gain unauthorized access while hiding its existence. Each of these categories serves a distinct purpose that differs from what a Trojan does, highlighting the unique nature of Trojans in the realm of computer security.