Slightly off-topics but I'd like to know if there is some kind of turn-key solution for small business or home use which uses a Raspberry Pi with attached USB H

Slightly off-topics but I'd like to know if there is some kind of turn-key solution for small business or home use which uses a Raspberry Pi with attached USB HD, that connects to other PCs via the network and pulls the files to be backed up. The idea being that the Pi and the HD themselves are never writeable from the outside and thus can't be encrypted themselves, 1) if using some suitably long retention time for older backups and 2) some kind of semi-smart monitoring system that can give warnings like "Hey, your data changed a lot suddenly. Might wanna have a look at that".