Conficker Worm - F-Secure estimates almost 9 million infections
If you have friends or family who might not be versed in applying Windows Updates, you may want to share with them how they can become safe from this rapidly spreading attack.
Calculating the Size of the Downadup Outbreak
http://www.f-secure.com/weblog/archives/00001584.html
http://www.f-secure.com/weblog/archives/00001582.html
QUOTE: The number of Downadup infections are skyrocketing based on our calculations. From an estimated 2.4 million infected machines to over 8.9 million during the last four days. That's just amazing.
Microsoft - Windows Update Web Site
Microsoft - Security at Home (learn security basics)