Microsoft calls the feature Controlled Folder Access and it is available in the Windows Defender Security Center under Virus & Threat Protection Settings. When this feature is enabled, only approved apps can access unprotected files and folders. By default, all your Library folders are protected which include Documents, Pictures, Videos, Music, Favorites, and Desktop folders for each user defined on the system. Additional folders can be added.
If an app that isn’t known attempts to make a change to any file in protected folders, it is blocked, blacklisted, and you are notified. If it turns out the app is legitimate, you can then mark it as safe.
This new feature should prove to be very effective in blocking ransomware. Unfortunately, for some strange reason, this feature is disabled by default. So, once your Windows 10 computer updates to 1709, be sure to locate this feature and turn it on.
If you are running a version of Windows other than 10, check out the free software RansomFree at https://ransomfree.cybereason.com. Also, make sure your antivirus program includes ransomware protection features.