What Is the Difference between a Worm and a Trojan Horse?

This is an entry-level question of definitions. A Trojan horse is a malicious application disguised as a legitimate application. After being installed, it enables a remote user to compromise a system. Usually transferred via Web downloads or e-mail, the compromise is made after a user installs or executes the application. A worm differs from a Trojan horse in that it replicates itself. This autonomous behavior
allows worms to quickly propagate and infect peer hosts. Trojan horses and worms are typically spread through e-mail attachments.

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