This paper discusses the evolving nature of malware and introduces the team of antimalware researchers in the Microsoft Malware Protection Center (MMPC), which helps keep computers and systems free of malicious and potentially unwanted software around the world. Research and development work at the MMPC supports a wide range of Microsoft products and services that run on more than 600 million computer systems worldwide every month. Analyzing data from those systems provides a high level of insight and enables the MMPC to quickly and effectively respond to malware outbreaks wherever and whenever they occur.