Please Note - this is a critical action that permanently alters the data on the file system, therefore we recommend contacting support for assistance in this process.
If you've experienced a virus attack or ransomware attack, you may need to rollback the file system to a previously known good. You need to know when the attack actually occurred so you can rollback before that point. It is best to issolate your network during this process with an "air-gapped" machine to ensure safety.
You can look through your snaps with Windows "Previous Versions" or following the "Clone" operation detailed here - there is most likely a snap just before the attack that has your unchanged data from that "moment" protected.
And ultimately if you have to ROLLBACK the entire file system to a snap point just before the attack where you know the data is good, you use the ROLLBACK feature in the Snapshots menu. This is a permanent rollback and all snaps since that point in time get deleted during the process. The rollback takes some minutes to perform.