From the KnowledgeBase
Why your computer will get infected with a virus and what to do about it
1. Your computer does not have antivirus software installed. Install antivirus software. 2. Your antivirus software does not have the most recent virus definitions. Update your virus definitions. 3. Your PC is behind in its Windows Updates. Bring your computer up-to-date. 4. You have allowed a file sharing program to set a folder on your computer as accessible by anyone, allowing a virus or worm to take over your hard drive. Uninstall the file sharing program, or disable sharing completely. 5. You click on links in e-mail without questioning the source of the e-mail (did you really expect to receive that message asking you to follow a link?) Consider the source of the e-mail before following links from it. 6. You have left the administrator password on your Windows computer blank. Set a new, secure administrator password. 7. You click on links in Instant Messenger (AIM) without asking if the sender actually meant to send it to you. Do not click on links in Instant Messenger until until you are sure it will not cause damage. 8. You allow Spyware programs to run on your computer. Get rid of them. 9. You download what you think is a notice about a free gift, but it actually is a virus file and it takes over your computer. Do not open files that you have downloaded before you have run a virus scan on them. 10. You open e-mail attachments that you didnít expect to receive. Do not open unexpected attachments, even if they are from people you know.
May 9, 2011