We had that happen at a company I worked for. Someone blindly opened an "invoice". We were back to work within a day. For each computer, a full malware scan and then back online. Dumped the one hard drive which was infected.
The NAS (which used to be writable to the victim) took a few days to restore from Amazon Glacier. To me this is key: always have an offsite backup which can't be erased by a non-admin. Use BackBlaze, CrashPlan, S3, Glacier, B2, Arq or whatever. Backups forgive a lot of stupid user sins.
That's why we wiped any system which showed sign of infection. Keep in mind this was ransomware so... probably... it is reasonable to assume the infection will not be subtle.
A local backup can be a lot quicker due to transfer times. From the local backup I'd then do an offsite. You can try to use snapshots with your NAS to just restore the most recent data from remote, too.
And this highlights the fallacy that Amazon Glacier is a backup service. It's not - it's an archive service. Something that takes a few days to recover is not backed up.
I agree the other products are indeed backups as they provide immediate recovery.
Before we instituted the Glacier backup, we discussed whether or not a few days or weeks time would be "good enough" for our needs. We decided it was.
So I totally agree that before picking a backup system, one needs to evaluate what the recovery is going to be like, and whether it will be good enough. For example, when recovering from the cloud, how long will it take to transfer all the data through your Internet connection? BackBlaze's overnight restore via FedEx could be a critical feature in your recovery speed.
The NAS (which used to be writable to the victim) took a few days to restore from Amazon Glacier. To me this is key: always have an offsite backup which can't be erased by a non-admin. Use BackBlaze, CrashPlan, S3, Glacier, B2, Arq or whatever. Backups forgive a lot of stupid user sins.