For systems that have already been affected by the ransomware, there is no decryption tool yet. As a post on TechNet points out: "The exploit code used by WannaCrypt was created to work only against unpatched Windows 7 and Windows Server 2008 (or earlier OS) systems, so Windows 10 PCs are not affected by this attack".
More than 45,000 WannaCrypt attacks have been recorded around the world, including in the UK, US, Russia, Ukraine, India, China, Italy, Spain, and Egypt.
Wannacrypt ransomware demands $300 in Bitcoin for unlocking encrypted files - a price which doubles after three days.
Many of the NHS computers affected by the ransomware on Friday were not updated, according to media reports.
Cybersecurity researchers have suggested the ransomware attacks are so potent because they exploit a a known software flaw dubbed EternalBlue. Microsoft has made the decision, which they say is unusual, but is regularly seen during these high profile attacks, to provide a security update which includes Windows XP, Windows 8, and Windows Server 2003.
Redmond released patches for Windows Server 2003 (SP2 x64 / x86); Windows XP (SP2 x64, SP3 x86); Windows XP Embedded (SP3, x86); as well as the 32-bit and 64-bit versions of Windows 8. Will your business be next?
The US technology giant Microsoft said in a statement on Friday it had identified and patched its operating systems against malicious software called WannaCrypt that is affecting computer networks in as many as 74 nations.
The operating systems are Windows XP, Windows 8, and Windows Server 2003.
Calling the attacks "painful", Phillip Misner, Principal Security Group Manager Microsoft Security Response Center, said Microsoft was worked throughout the day to protect their customers.
"Many of our customers around the world and the critical systems they depend on were victims of the malicious "WannaCrypt" software", the company said in a blog post.
Meanwhile, . The National Cyber Security Centre has issued a statement to say it is "working round the clock with United Kingdom and worldwide partners and with private sector experts to lead the response to these cyber attacks".