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Microsoft Security

Latest data shows newer versions of Windows have lower malware infection rates than older versions

We released the latest volume of the Microsoft Security Intelligence Report last week. The latest data on how different versions of the Windows operating system are mitigating modern malware attacks suggests that newer versions are performing better than older versions.

The figure below illustrates the malware infection rates for Windows client and server operating systems in the third and fourth quarters of 2014 based on data from hundreds of millions of systems worldwide. This data is normalized, meaning the infection rate for each version of Windows is calculated by comparing an equal number of computers per version; for example, comparing 1,000 Windows Vista Service Pack 2 (SP2) based systems to 1,000 Windows 8.1 based systems in the fourth quarter of 2014 we can see 5.2 Windows Vista based systems infected with malware compared to 1.3 Windows 8.1 systems infected. In percentage terms, that’s equivalent to 0.52% of Windows Vista based systems (5.2/1,000*100 = 0.52) compared to 0.13% of Windows 8.1 based systems (1.3/1,000*100) infected with malware.

Figure: Infection rate by client and server operating system in the third and fourth quarters of 2014 (3Q14/4Q14)

The newest versions of both Windows client and server operating systems had the lowest malware infection rates during the period, by a large margin.

Some of the CISOs and IT professionals I talk to use this operating system infection rate data to help make a business case for upgrading to newer, more secure software or deploying more secure service packs for their current platforms. As you can see from the latest data, newer is better across the board.

You can download this data in volume 18 of the Microsoft Security Intelligence Report at

Tim Rains
Chief Security Advisor
Worldwide Cybersecurity & Data Protection