If you’ve got a Synology NAS open to the Internet (i.e: so you can access your files away from home via the Internet), disable that feature and make sure your firewall totally blocks the NAS from talking to the Internet. There’s a nasty bit of ransomware going around targeting Synology NAS units – it encrypts the volumes on the NAS and makes you pay the attacker via Bitcoin in order to get the encryption passphrase to access your files again.