nas 326

I'm afraid you are the victim of a ransomware attack. More here.

That is possible. The files are still there, but encrypted. Maybe a decryptor is available here, but your extensions point to C3RB3R ransomware, which isn't in the list.

There should be a readme somewhere. The criminals want you to pay ransom, in which case you should know how. Maybe that readme discloses another type of ransomware, for which a decryptor is available.

I don't know where to search for that readme. The infection isn't necessarily on the NAS. It could also be on (one of) the clients which have access to the shares. Actually the description of the C3RB3R tells it's a Windows only virus, which in that case cannot run on the NAS. But of course the criminals won't supply release notes of new iterations of their scam.

I advice you to run a deep scan on all clients with (write) access to that share, to see if they are infected, and maybe get a name of the virus. There are no scanners available to run on the NAS. But if you have shell access 'top' might tell if there is a strange process running.