                     You can't see it and you may not necessarily know when it has
                     struck--until it's too late. They are the many types of malicious
                     code--more commonly known as viruses and worms. They can
                     cripple your computer and wreak havoc on your personal files.
                     They have many names, and we'll look at the most common in
                     this guide. At last count there were more than 53,000 virus threats
                     on the loose. They are looking for you, so be sure to find them
                     first!

                     What is a Virus?
                     A virus is a program that infects systems by rewriting files, or by
                     inserting or attaching a copy of itself to a file (including email
                     files). When an infected file is opened, the embedded virus is
                     executed. Often, users don't realize that this is happening in the
                     background. It may replicate itself within one computer, but to
                     infect other machines, it must be passed on in a program, email
                     file or attachment, infected diskette or other "removable media,"
                     although it can't spread itself from computer to computer without
                     help.

                     What a Virus Can Do
                     A virus can do as minimal damage as copying itself and then
                     allowing programs to run normally. Most, however, do far more
                     damage, by delivering a "payload." For example, they could
                     display a certain message on the machine's monitor, perform a
                     deletion or modification to a certain file or files, delete entire files,
                     or even reformat your hard drive.

                     Mobile Code
                     Mobile code is actually programming that specifies how
                     applications exchange information. It was created by and for Web
                     developers who use it to write applications that Web browsers can
                     automatically download and execute. However, it can also be
                     used as a weapon in computer warfare. Once downloaded onto
                     your system, hackers can transmit data from your computer back
                     to their computers without your knowledge. They can steal your
                     passwords or credit card information, erase or transfer important
                     files, and even render your system inoperable.

                     Common Forms of Mobile Code
                     Java applets are auto-executable programs written in the Java
                     programming language (originally developed by Sun
                     Microsystems). Java applets can perform any number of tasks,
                     and can be embedded in Web pages or sent as email
                     attachments. Since most Web browsers are set to automatically
                     run Java applets, applets which are malicious in nature can be a
                     serious threat. It is possible to change the settings of your Web
                     browser to alert you before executing any Java applet.

                     ActiveX controls, sometimes similar to Java applets but based
                     upon a technology originally developed by Microsoft, have total
                     access to the Windows operating system, which makes them
                     very potent and sometimes more dangerous than even Java
                     applets.

                     Macros are languages that, when embedded in files, can
                     automatically execute software commands without user
                     knowledge. 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 is not technically a "virus"
                     because it can reproduce itself independently. A good example of
                     this was the ILOVEYOU email worm, which automatically emailed
                     itself to everyone in the recipient's address book. A worm can
                     spread itself to hundreds of thousands of machines very quickly
                     via the local networks and the Internet.

                     The term "zombie" has come to mean a computer secretly
                     implanted with a dormant program to be awakened later to aid in a
                     collective attack on another system. 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.

                     Hoaxes
                     There are 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. We will provide you with the latest information on real
                     viruses as well as hoaxes, and give you immediate anti-virus
                     updates to protect your computer against any new threats.

                     How Does Malicious Code Infect Your Computer?
                     Now that you've learned of the different types of code to watch out
                     for, how does it actually get to your machine? Dangerous code
                     can get onto your system and wreak havoc through a number of
                     different channels. Mobile code can travel by itself; it just needs
                     an open pipeline - which is why broadband connections so often
                     fall prey to it. Other types of viruses though, are stowaways. The
                     two best avenues for this type of virus or infected code to travel are
                     through downloads from Web sites, via email or in email
                     attachments.

                     Virus Prevention
                     Never open email from people who you don't recognize, and
                     download only from sources with which you are familiar. Scan all
                     email attachments and downloads before opening them. And,
                     since new viruses are created daily, update your virus definitions
                     frequently.