Before we get to what Norton Antivirus does, it might be a good idea to define some terms that we think we sort of know about but are afraid to admit ignorance of.

What is malware?

Malware is any software that is created with malicious intent, thus the combination of the work "malicious" with the word "software" to get "malware."

What is a virus?

In the human body a virus replicates itself and spreads through the body, making us sick. It also infects others.

A computer virus is a program that makes the computer "sick." It replicates itself and spreads to other computers. It is a program that tries to alter the behavior of the computer without the user's permission. For example, it might try to overwrite data, change the way a program works, or alter system files.

What is a worm?

There is disagreement among computer experts as to the exact definition of "worm," but a worm is a virus that is a stand alone program whereas a regular virus attaches itself to other programs. It does no direct damage but mails itself to other computers from which it mail copies of itself until there are such large numbers that networks can get jammed up.

What is a trojan horse?

A trojan horse is not a virus but it may carry them. Like the Trojan horse of antiquity it presents something very attractive and pretends to be something it is not. It comes in on freeware programs that then install hidden applications. They don't run on their own but trick the user into running them. They can't replicate themselves but they can incorporate a worm and send themselves to other computers.

What is phishing?

Phishing is not a danger to your computer but it does threaten your identity. It's an e-mail that looks exactly like something from your bank, for example, but it may take you to a site where it asks for your social security number, your driver's license number and other information useful for stealing your identity.