Microsoft: Windows XP infected twice as frequently as Windows 7
Source: Microsoft SIR Microsoft's Security Intelligence Report for the first half of 2012 reveals that the company has to remove malware from systems running Windows XP twice as frequently as from systems running Windows 7 or Vista. In the report, the company says that its Malicious Software Removal Tool (MSRT) discovered an infection on around one per cent (9.5 in 1,000) of scans under Windows XP. On later versions of Windows, this figure drops to approximately 0.5 per cent.
There are, however, several reasons for taking Microsoft's statistics with a pinch of salt. Firstly, MSRT cannot identify all malware, instead limiting itself to malware that Microsoft is taking a particular interest in (for reasons such as it being a particularly widespread distribution). Secondly, Microsoft's figures also include programs which, though they may not be particularly welcome, can't really be described as malware. For example, the report states: "The most commonly reported threat family in 1H12 was Win32/Keygen." Under this designation Microsoft includes a range of different programs used "to generate keys for various software products."
Source: Microsoft SIR The "dangerous" keygens were also the most commonly reported software in Microsoft's previous Security Report. Microsoft avoids the word "malware" in relation to keygens, but it does use the term "threat", which is equally hard to justify. The authors, however, give it their best shot, describing hazards associated with illegal software use. Nonetheless, the impression remains of a lack of consistency in terms of defining who exactly is threatened by what.
What is interesting, however, is that programs categorised as trojans, and therefore unambiguously malicious, have now pulled further ahead of those categorised merely as potentially unwanted software. The 13th Security Intelligence Report is available to download free of charge as a 146 page PDF.