Protect a Windows Computer from NotPetya/SortaPetya/Petya Ransomware
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1.  Use a Windows computer and create a text file with a few words
    as perfc.txt

2.  Save it in the C:\Windows folder as perfc.txt
    Thus Windows Explorer locates C:\Windows\perfc.txt

3.  Rename the file as perfc
    Thus Windows Explorer locates C:\Windows\perfc

4.  Right-mouse on the file and choose properties.

5.  Check the box for Read-only and click OK.

This fix will work only for this computer and will not mitigate
spread of the ransomware throughout the network.  This fix must be 
made on all Windows computers of the network to protect the network.