Malicious software infection rates differ significantly for different versions of the Microsoft Windows operating system. Windows Vista was less infected at any service pack level than Windows XP. Comparing the latest service packs for each version, the infection rate of Windows Vista SP1 is 61.9 percent less than that of Windows XP SP3.



The following map illustrates the infection rates of locations around the world, expressed in a metric called CCM that represents the number of computers cleaned per thousand executions of the Malicious Software Removal Tool.



Despite the global nature of the Internet, there are significant differences in the types of threats that affect users in different parts of the world. Infection data from several Microsoft security products for some of the more populous locations around the world demonstrates the highly localized nature of malware and potentially unwanted software.

The figure below shows the relative prevalence of different categories of malware and potentially unwanted software in the eight locations with the most computers cleaned in 1H09, expressed as percentages of the total number of computers cleaned in each location. (The sum of the infection rates for each location may exceed 100 percent because some computers have more than one category of threat removed from them during each time period.) See page 40 in the Security Intelligence Report for an explanation of the categories used in this figure.