Bitdefender constantly displays warnings that C:\ProgramData\BOINC\projects\boinc.bakerlab.org_rosetta\rosetta_4.15_windows_intelx86.exe is showing ransomware behaviour. Encrypted files are:
- boinc_checkpoint_count.txt
- csd_atom_properties.txt
- Default-5StepDown.txt

Why is Boinc trying to encrypt files??

BOINC isn't encrypting anything.
The files you refer to are made by the Rosetta science application, for storing a checkpoint, and progress of its files.

But this is essentially why we ask that you exclude the BOINC data directory from being actively scanned by your anti virus program. Set up a DMZ. Because a lot of what the science applications for the various projects do can be seen as suspect behaviour.

Only scan the data directory by hand when you aren't running BOINC.
And report any false positives, such as these, to Bitdefender and Rosetta.

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