Microsoft have issued patches for previously unsupported operating systems alongside the following statement :-
Many of our customers around the world and the critical systems they depend on were victims of malicious “WannaCrypt” software. Seeing businesses and individuals affected by cyberattacks, such as the ones reported today, was painful. Microsoft worked throughout the day to ensure we understood the attack and were taking all possible actions to protect our customers. This blog spells out the steps every individual and business should take to stay protected. Additionally, we are taking the highly unusual step of providing a security update for all customers to protect Windows platforms that are in custom support only, including Windows XP, Windows 8, and Windows Server 2003. Customers running Windows 10 were not targeted by the attack today.
We also know that some of our customers are running versions of Windows that no longer receive mainstream support. That means those customers will not have received the above mentioned Security Update released in March. Given the potential impact to customers and their businesses, we made the decision to make the Security Update for platforms in custom support only, Windows XP, Windows 8, and Windows Server 2003, broadly available for download (see links below). This decision was made based on an assessment of this situation, with the principle of protecting our customer ecosystem overall, firmly in mind.
In March, we 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, we suggest you immediately deploy Microsoft Security Bulletin MS17-010.
Download English language security updates:
To download localized versions for the security update for Windows XP, Windows 8 or Windows Server: http://www.catalog.update.microsoft.com/Search.aspx?q=KB4012598
General information on ransomware: https://www.microsoft.com/en-us/security/portal/mmpc/shared/ransomware.aspx
MS17-010 Security Update: https://technet.microsoft.com/en-us/library/security/ms17-010.aspx