Once downloaded or executed, the macros have total access to the user's files, and can perform system modifications specified by the code writer. Many Windows-based macros are written in Visual Basic. Similar in many ways to Netscape's JavaScript, VBScript is a Microsoft scripting language that makes it possible to embed interactive elements in HTML documents. A worm is a program that can actually propagate itself without requiring user interaction. A worm can spread itself to hundreds of thousands of machines very quickly via the local networks and the Internet.
Zombies are a relative newcomer to the playing field.
A Trojan Horse is a malicious program that pretends to be a benign program, such as a screen saver, game or other type of utility. It does not replicate itself like a virus, does not make copies of itself like a worm and is usually spread by email or Web downloads. Thereare new viruses being discovered all the time, but at the same time, there are many rumors of viruses and other types of malicious code that do not actually exist. There are enough of these, however, that we keep track of them and provide a resource for you to double-check your information against the facts. To keep up on the latest threats to your system, real or imagined, check the Symantec AntiVirus Research Center on a regular basis.