A computer virus is a small programs that people write in order to be malicious or just to be recognized for there work. They pass from computer to computer like a biological virus passes from person to person. It must piggyback on top of some other program or document in order to launch and once it is running, it can infect the whole computer and can every erase your hard drive.
Ways your computer can get infected:
By opening an E-mail from someone you don’t know
By installing a program or file that has been infected
By downloading software, music & movie from internet, or from pirating websites.
Here are a few ways you can tell if you are infected: Your computer runs more slowly than normalYour computer stops responding or locks up oftenYour computer crashes and restarts every few minutesYour computer restarts on its own and then fails to run normallyApplications on your computer don't work correctlyDisks or disk drives are inaccessibleYou can't print correctlyYou see unusual error messagesYou see distorted menus and dialog boxes
Top 5 worst viruses:
The CIH virus in 1998: Estimated Damage $20 to $80 million worldwide and countless amounts of PC destroyed
Melissa in 1999: Estimated Damage $1 billion
ILOVEYOU in 2000: Estimated Damage $5.5 to $8.7 billion and about 10 % of all internet connection computer where
Code Red in 2001: Estimated Damage $2 billion
SQL Slammer in 2003: Estimated Damage shut down South Korea’s internet for 12 hours and infected 500,000 servers worldwide