Historically, computer Trojans (Trojan horses) have been defined as a class of threats which attempt to present themselves as useful programs and thus trick users into running them.

Since Trojans are a very broad category, it is often divided into several subcategories:

DownloaderMalicious programs with the ability to download other threats from the Internet.

DropperMalicious programs with the ability to drop other types of malware onto compromised computers.

BackdoorMalicious programs which communicate with remote attackers, allowing them to gain access to the computer and take control over it.

Keylogger – (keystroke logger) – A program which records each keystroke that a user types and sends the information to remote attackers.

Dialer – Malicious programs designed to connect via premium-rate numbers instead of the user's Internet service provider. It is almost impossible for a user to notice that a new connection was created. Dialers can only cause damage to users with dial-up modems, which are no longer regularly used.

If a file on your computer is detected as a Trojan, it is advisable to delete it, since it most likely contains nothing but malicious code.