Computers usually get infected through email attachments, Internet downloads, instant message attachments, and other types of network based file exchange. Malicious code can also be triggered simply by visiting a website or viewing a message in the preview pane of your email program. You should also be cautious whenever you insert or attach anything that can copy files to your computer, such as a CD, DVD, or portable disk drive.  You should have good anti-virus and firewall software to minimize your risk.