Trojan horse: A Trojan horse is so named because it is much like the Greek legend of the Trojan horse. The legend tells of the Trojan war, a war between the Greeks and Trojans. The Greeks being unable to take the city of Troy, instead left a huge wooden horse outside the gates. The Trojans, after the Greeks had left, brought the huge statue inside their gates. The horse was filled with Greek soldiers. After dark, the Greek soldiers emerged from the horse and captured the city. This is also where the phrase "Beware of Greeks bearing gifts," comes from.

A Trojan horse on a computer is a small program which you are persuaded into installing on your machine. It may masquerade as something else. One of the more flamboyant examples of this was Happy 99. This was sent around on New Year's Day of 1999, and it seemed to be a very lovely fireworks display when you clicked on it. A lot of very knowledgeable folks got fooled by this one and sent it around to their friends before anyone ever discovered that it also modified system files, and sent itself out to addresses it found in the computer's address book. Because it propagates itself in this fashion (sending itself to others), it is also a worm.

Virus: A virus is computer code that inserts itself into another program's code. It does not exist on its own, it becomes part of another executable file. It replicates its code into other executable files. These executables, or programs, then behave differently, often destructively, and can destroy data files opened with the program. A virus must exist inside of executable code. *See Sidebar.

Window: What exactly is a Window? It is a rectangular shaped box that you see on your computer screen when you open a program or document. It has very specific parts, and each of these parts has its own special characteristics. You are looking at a Window right now as you read this. If you are reading this in Internet Explorer, you will notice at the top of the window there is a bar that says, "Glossary T-Z - Microsoft Internet Explorer." That bar is called the Title Bar, because it shows the title of the page you are viewing and the application (program) you are viewing it in. On the right of the Title Bar you see three little buttons, the farthest right being an X. These are called Control Buttons. You can close the application with the X. For more information, see our article on the Parts of a Window.

Wizard: A wizard is a set of windows with simple instructions to follow in a step-by-step procedure. You may answer a question, then click Next, or make a selection of some sort, then click Next. Wizards are good, they walk you through doing a more complex task by breaking it down into simple steps.

Worm: A worm is a destructive computer program that infects and worms its way into and around a computer network, propagating itself from machine to machine, generally by sending itself out in emails.

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