Computer viruses are malicious programs designed to cause annoyance and even damage to computer data. They spread by infecting files or by automatically sending e-mails to everyone in your address book.
What Can I Do About Them?
First of all you should try to be careful when opening e-mail attachments. Many viruses are spread as files attached to e-mails, often trying to lure you into opening them with titles like 'Open me' or 'You have won..'.
You may even receive a virus mail from someone you know, who won't even know that the mail has secretly been sent from their account by a malicious virus program. As a general rule, you shouldn't open an e-mail attachment unless you are expecting to receive one and you know who it's from.
Make sure you all ways have antivirus protection. Keep it updated and scan with it regulary.