Perhaps you have heard of computer viruses in the news, but do you know what a virus is? A virus is a bit of programming code meant to cause some unexpected and usually undesirable effect. (You use legitimate programs all the time, like a card making program to create personalized greeting cards.  A virus is the same thing, except it invades your computer without permission and, instead of creating cards or picture albums, does something bad.) Some viruses are playful and innocuous - maybe displaying a joke on the screen. Other viruses can be devastatingly harmful - deleting files, stealing passwords and credit card numbers, erasing your hard drive, or even causing your hard drive to be reformatted. It's vandalism to your computer.

Most viruses come from the Internet and email these days. but they could come from an infected floppy disk or from programs that you have downloaded from a website. Often the person passing on the virus is unaware that the file is infected. Sometimes the virus lies dormant until a pre-determined circumstance (such as a date) causes it to execute.

Not all viruses come through email.  Many people say, I only open mail from people I know.  That's no protection.  Emails can look like they come from someone you know...even if they do not.

Emails with viruses are commonly "spoofed".  Spoofing is sort of like putting a fake return address on an envelope.  It comes from someone different than it appears to come from.  Spoofed email does the same thing.