Microsoft has taken the rare step of issuing a fix for versions of Windows it had previously “retired”, in an attempt to halt the global spread of the malware that hit the UK’s National Health Service on Friday.
Though technically no longer supported by the company, the software — including the once highly popular Windows XP — is still in use on some PCs, leaving users exposed to attacks. Just under 5 per cent of devices in the NHS still run XP, according to NHS Digital. The world’s biggest software company released the patch, or repair, late on Friday night in the US, after a flaw in Windows was found to provide the door through which the malicious code had infiltrated computers across the globe.
Microsoft usually drops support for older versions of Windows — meaning it no longer releases repairs for problems that are found in the software — after a decade or more. Support for Windows XP ended in 2014, some 12 years after the software was introduced. But an estimated 7 per cent of the world’s PCs still run on the software, according to NetMarketShare. With more than 1bn PCs believed to be in use, that amounts to some 70m machines.
Microsoft issued a patch at the time that could be applied to current versions of Windows, and Mr Misner said that would have protected users against WannaCry, provided they installed the fix on their machines.
Overnight on Friday, Microsoft said it had taken the “highly unusual step” of issuing a new patch, this time designed to work with unsupported versions of its operating system. The fix is designed for Windows XP, as well as Windows 8 — support for which ended in 2016, only four years after the code was launched — and Windows Server 2003.
“It’s probably the worst we’ve seen in a very, very long time,” said Mounir Hahad, a senior director at CyphortLabs. “This has a means of spreading so fast to a lot of organisations — and then horizontally, within organisations.”
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