There is a new ransomware worm going around called WannaCry that exploits a previously unknown backdoor in Windows. This vulnerability has been patched. Make sure your Windows OS is up to date to ensure that you are no longer vulnerable.
As usual, please be careful what you access online. Barring that, keep local and/or cloud backups for your computer and keep your antivirus and antimalware programs up to date to prevent catastrophic loss of data on the off chance of infection. Stay safe, everyone.
Concise summary of details in this video: https://youtu.be/ibLaCEL8E4E
More technical information, thanks to Starhammer: https://www.askwoody.com/2017/how-to-make-sure-you-wont-get-hit-by-wannacrywannacrypt/