A Trojan horse in computer language is not a virus but related to viruses by being an often harmful program. Trojan horse programs got their name because they pretend to be other computer programs such as games, file sharing programs or even an email attachment. Just opening or downloading a Trojan horse file won’t activate it but running it will – playing the game or opening a spreadsheet in Excel. You need to be aware of Trojan horse programs because they can delete your files or crash your computer system. At their worst, these programs are used for can be used to steal your passwords or to commit electronic money theft.