You usually need to see a doctor when you are very sick. The doctor may find that you have a virus. You will probably get a special medicine to stop the virus from spreading through your body's systems. This will help your body become healthy enough to get rid of the virus. It is good you can take a medicine to get rid of your virus.

Sometimes, computers also become infected with a computer virus. This kind of virus can affect your computer's systems so badly that the computer's entire operating system can fail. There are some things you can do to make your computer "well" again before its systems fail.

The doctor may even tell you that you must stay out of school for a few days because your virus could infect other students. A virus inside one computer can only infect other computers if the virus is carried in floppy disk between computers or through e-mail sent from the infected computer.

There are four common ways a virus can be spread. The virus can be hidden inside a program. It cannot affect the computer until the program is opened in the computer. Every time the program is run (opened), the virus can get into the computer and spread through its systems.

A computer can also get into a computer through E-Mail. Normally, the only way the virus can affect your computer is when files attached to the E-Mail message are opened. This kind of virus can E-Mail itself to other people listed inside the E-Mail address book in that computer.

Another way a virus can spread is as a "worm" in the computer. This kind of virus moves mostly through computers connected to a network. A "worm" should never be able to enter a computer not connected to the Internet or a network. It will infect and damage every computer it enters. One reason it is called a "worm" is because it moves through "holes" in a network's security features.

Viruses also hurt computers when they enter as a "Trojan Horse." This virus is a computer program that convinces you it will do one thing (such as let you play a game on your computer) but causes damage to the computer when the program is opened. It may even erase your hard drive.

Is there something you can do to protect your computer? Sure! You can install an "anti-virus" program. This program can check every file in your computer for viruses. It will let you know when a new virus enters your computer. The program can even help you restore a computer if it gets infected with a virus.

Another way to protect your computer is to never open an E-Mail attachment unless you know and trust the person who sent E-Mail to you. Also, you should always be very careful when you download files from the Internet. Virus makers hide viruses inside these files.

NASA and KSNN want you to know we make sure our files are not infected by a virus. We want you to enjoy visiting our website and opening our files to learn more about computers and science.