As many Windows users around the world and critical systems they depend on were victims of the malicious "WannaCrypt" software, Microsoft has released a patch for the unsupported systems - Windows XP, Windows 8 and Windows Server 2003.

In March, Microsoft released a security update which addresses the vulnerability that these attacks are exploiting. Those who have Windows Update enabled are protected against attacks on this vulnerability. For those organizations who have not yet applied the security update, Microsoft suggests to immediately deploy Microsoft Security Bulletin MS17-010.

For Microsoft's customers using Windows Defender, Microsoft released an update earlier today which detects this threat as Ransom:Win32/WannaCrypt.

For those still running versions of Windows that no longer receive mainstream support, Microsoft made the Security Update for platforms in custom support only, Windows XP, Windows 8, and Windows Server 2003, broadly available for download here.

Extortionist hackers who may be using leaked computer exploits from the U.S. National Security Agency infiltrated computers in dozens of countries in a fast-spreading attack initiated on Friday.

The ransomware used in cyber-attacks encrypts files and demands that victims pay $300 in bitcoin for them to be decrypted. The malicious software has infected more than 75,000 computers in 99 countries worldwide on Friday, most of them concentrated in Russia, Ukraine and Taiwan, according to Dutch cybersecurity company Avast Software BV.

The attackers were exploiting a vulnerability in Microsoft software that was patched in March. Attack code targeting that vulnerability was released publicly by Shadow Brokers, a group that has been leaking stolen hacking tools purportedly from the NSA.