Microsoft: Conficker worm infection detected on 1.7 million systems by Microsoft researchers in the last half of 2011. Microsoft: All cases of Conficker infection stemmed from two attack methods: weak or stolen passwords and exploiting software vulnerabilities for which updates existed. Conficker has remained at the top of the enterprise threat list for the past two and a half years, the study says. The report includes a graphic listing some of the passwords that Conficker tries when it’s on a machine inside the enterprise trying to get into file shares.”]