Your computer can get a virus just like your body can be invaded with a virus making you (or your computer) sick. A virus can wipe out information on your computer and create major havoc. Viruses usually originate from malicious people. You can unintentionally download virus from a web site or get it from a disk that someone has lent you. There are virus-checking programs, but there are new viruses popping up every day. So the best defense against a virus is to be very careful not to download programs or data from a site you're not familiar with.