Alex Pankratov :
Oct 26, 2018
You can disable USB drive pretty easily already by enabling device ejection at the end of a backup - https://bvckup2.com/support/forum/topic/827
It is also possible to "un-eject" a drive that is still connected, though it gets hairy because it requires disabling and then re-enabling underlying mass storage device, which may lead to some nasty side-effects.
Another option is to switch bvckup2 into service mode and lock down the write access to your USB device to service's user account only. Though it's possible that a cryptoware can remove restrictive access permissions from the file system objects, at least in theory.