From the security experts at Wordfence, now is a good time to make sure your Windows software is updated. According to their post, a Massive Global Ransomware Attack Underway, Patch Available.
The article explains the following on how to protect yourself (the emphasis is mine):
According to Microsoft a fix for this vulnerability was released on March 14th for all affected versions of Windows. If you are running Windows and have automatic updates enabled you should be okay. If you don’t and haven’t updated recently you should update to the most recently released version immediately. It is important to note that unsupported versions of Windows, like XP, did not receive this security update. Those systems should either be isolated or shut down.
For a complete explanation of this attack, check out the article linked above.