Trojan

A Trojan is a virus obtained over a computer.  When received, for example, by email they appear to be a legitimate email: sometimes they may even appear to be from a friend or a business that you are affiliated with. Despite appearing to be harmless, once opened they may install a virus onto the user’s hard drive.  A major problem with this is that not only does it give your computer a virus; it is also not always instantly recognized.