From Ars Technica
Eight days ago, the WCry ransomware worm attacked more than 200,000 computers in 150 countries. The outbreak prompted infected hospitals to turn away patients and shut down computers in banks and telecoms. Now that researchers have had time to analyze the self-replicating attack, they're learning details that shed new and sometimes surprising light on the world's biggest ransomware attack.https://arstechnica.com/security/2017/05/windows-7-not-xp-was-the-reason-last-weeks-wcry-worm-spread-so-widely/Chief among the revelations: more than 97 percent of infections hit computers running Windows 7, according to attacks seen by antivirus provider Kaspersky Lab. By contrast, infected Windows XP machines were practically non-existent, and those XP PCs that were compromised were likely manually infected by their owners for testing purposes. That's according to Costin Raiu, director of Kaspersky Lab's Global Research and Analysis Team, who spoke to Ars.
While the estimates are based only on computers that run Kaspersky software, as opposed to all computers on the Internet, there's little question Windows 7 was overwhelmingly affected by WCry, which is also known as "WannaCry" and "WannaCrypt." Security ratings firm BitSight found that 67 percent of infections hit Windows 7, Reuters reported.
The figures challenge the widely repeated perception that the outbreak was largely the result of end users who continued to deploy Windows XP, a Windows version Microsoft decommissioned three years ago. In fact, researchers now say, XP was largely untouched by last week's worm because PCs crashed before WCry could take hold. Instead, it now appears, the leading contributor to the virally spreading infection were Windows 7 machines that hadn't installed a critical security patch Microsoft issued in March
The Kaspersky figures are illuminating because they show Windows 7 x64 Edition, which is widely used by large organizations, being infected close to twice as much as Windows 7 versions mostly used in homes and small offices. It's not clear if that means enterprises are less likely to patch or if there are other explanations.
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