1. Open your terminal app
  2. Type diskutil list and hit enter
  3. Note the disk volume of your bootcamp partition, (example: /dev/disk0s3)
  4. Next find the Volume UUID of your bootcamp partition by typing diskutil info /dev/diskXsY where X is your disk and Y is your bootcamp partition. i.e. diskutil info /dev/disk0s3
  5. The result will return information of Type (Bundle): ntfs and Volume UUID: XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
  6. Note both of those paramaters, and copy the Volume UUID into your clipboard.
  7. Type sudo vifs and enter your password
  8. Once in vifs, type ‘a’ and hit enter.
  9. Create a new line on the bottom of the page.
  10. Copy and paste this EXACTLY as it is printed here (except) replace the UUID with your UUID that you copied in step 6: 
# Forbid Mounting of Bootcamp volume at boot by uncommenting the line below
UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX none ntfs ro,noauto

11. Press escape, then hold shift and type zz to save the file.

12. Bootcamp will now be properly forbidden from automounting at MacOS Boot.