Restic is my current backup solution of choice and that takes snapshots by default. If you took a backup on Monday, ransomwared on Tuesday, your backup volume w

Restic is my current backup solution of choice and that takes snapshots by default. If you took a backup on Monday, ransomwared on Tuesday, your backup volume would double in size (file de-duplication is going to fail spectacularly), but the Monday backup will be unimpacted until a prune operation is run. Suggested prune workflow is to maintain fairly staggered snapshots eg: 1x six-months ago, 1x three-months ago, 3x from last month, whatever makes you comfortable. Which should give a pretty comfortable margin on retaining your files.