Data from Microsoft’s newest twice-yearly security report showed that in the second quarter of 2012, Windows 7 was between 33% and 182% more likely to be infected by malware than in the second quarter of 2011.

The infection rate for Windows RTM, or “release to manufacturing,” the original version launched in Oct. 2009, was 33% higher this year for the 32-bit edition (x86), 59% higher for the 64-bit (x64) OS.

Windows 7 Service Pack 1 (SP1) — the upgrade that shipped in Feb. 2011 — saw even larger infection increases: 172% for x86, 182% for x64.

Microsoft blamed several factors for the boost in successful malware attacks, including less savvy users.

Source: PCWorld