On Tuesday, Microsoft released volume 13 of its Security Intelligence Report, which revealed that while there has been an increase in the number of malware-infected Windows 7 SP1 and Windows XP computers; the number of Windows Vista SP2 systems infected by malware has witnessed a sharp decline.

The report - in which the prevalence of malware threat and infection rates for the 2012 first-half were reviewed - revealed that, on an average, a 23 percent and 7 percent year-on-year increase in malware infections was respectively seen in 32-bit systems and 64-bit systems of Windows 7 SP1 systems during the first half of this year.

In comparison, while there was a nearly 10 percent increase witnessed in the average number of malware-infected Windows XP SP3 machines during the first six months of 2012; the number of malware-infected Windows Vista SP2 PCs plunged 33 percent and 43 percent respectively for 32-bit and 64-bit PCs.

Elaborating on the sudden spate in malware infections in Windows 7 SPI systems, the report drew attention to a similar situation of a gradual increase in infection rates which was "observed for Windows Vista between 2007 and 2009, prior to the release of Windows 7."

Pointing out that increasing adoption of software delivers a blow to its security, the report said: "As the Windows 7 install base has grown, new users are likely to possess a lower degree of security awareness than the early adopters and be less aware of safe online practices."