New
#101
Here is the MS blog showing which have been patched:
Protecting customers and evaluating risk MSRC
The one being exploited by WCry is EternalBlue.
An NSA-derived ransomware worm is shutting down computers worldwide | Ars Technica
Being fully patched and up-to-date prevents this exploit, and the malware's kill switch has been activated. MS even put out fixes for unsupported platforms (XP, 8, Server 2003). But, systems that have already been hit need recovery.Another cause for concern: wcry copies a weapons-grade exploit codenamed Eternalblue that the NSA used for years to remotely commandeer computers running Microsoft Windows. Eternalblue, which works reliably against computers running Microsoft Windows XP through Windows Server 2012, was one of several potent exploits published in the most recent Shadow Brokers release in mid-April. The Wcry developers have combined the Eternalblue exploit with a self-replicating payload that allows the ransomware to spread virally from vulnerable machine to vulnerable machine, without requiring operators to open e-mails, click on links, or take any other sort of action.
EDIT: You'll want to research those patches to get the KB numbers, and then verify that the system does indeed have them installed.