Viruses

What I know:
 I know that a computer virus enter your computer because of the use of downloads and internet. This viruses can delete data form your computer, and cancel some of the functions of your computer.

What I wonder:

• How do viruses work?
• How to avoid viruses ?
• Is it true that Mac's can't have viruses?
• What to do if you have a computer virus? 
• What are some viruses? 

Useful links:

• http://www.microsoft.com/security/pc-security/virus-whatis.aspx
• http://support.microsoft.com/kb/129972
• http://www.howstuffworks.com/virus.htm
• http://www.runbox.com/email-school/what-are-computer-viruses-and-how-to-protect-against-them/
• http://www.us-cert.gov/reading_room/virus.html#virus
• http://computer.howstuffworks.com/macs/can-macs-get-viruses2.htm
• http://www.computerhope.com/issues/ch000737.htm
• http://antivirus-software.topchoicereviews.com/types-of-viruses.html

What I learned: 

• Computer viruses are often spread by emails, softwares, and other attachments 
• A worm is: this is a form of virus that spread within emails, then this "worm" takes information such as email addresses, and send other "infected" emails to your contacts. 
• A trojan horse is:  this virus hides inside real programs, then it enters a code inside the computer and lets hackers enter the information in the computer.
• A spyware: a virus that enters the computer and gets access to your personal information. It uses this information and can also change your actions in your own computer. 

I COULDN'T FINISH BECAUSE I HAD TO GO TO GYMNASTICS UNCOLI