Blocking attachments by hash

[DEZERTIR]

Good afternoon!
Could you please tell me if it's possible to block attachments by hash using standard tools?

 

[Onslow]

Only from your previous posts I have guessed you ask about mail .
So most likely about Proxmox Mail Gateway server.

As far as I know, PMG uses ClamAV, among others. So you can prepare for ClamAV a local signature with a hash of this attachment and ClamAV will recognize the file as "infected".
https://docs.clamav.net/manual/Signatures/HashSignatures.html

Anyway, I think you can ask questions about Proxmox Mail Gateway at its subforum:
https://forum.proxmox.com/forums/mail-gateway-installation-and-configuration.8/