What is everyone doing? SELinux? AppArmor? Something else?
I currently leave my nextcloud exposed to the Internet. It runs in a VM behind an nginx reverse proxy on the VM itself, and then my OPNSense router runs nginx with WAF rules. I enforce 2fa and don’t allow sign-ups.
My goal is protecting against ransomware and zerodays (as much as possible). I don’t do random clicking on links in emails or anything like that, but I’m not sure how people get hit with ransomware. I keep nextcloud updated (subscribed to RSS update feed) frequently and the VM updates everyday and reboots when necessary. I’m running the latest php-fpm and that just comes from repos so it gets updated too. HTTPS on the lan with certificates maintained by my router, and LE certs for the Internet side.
Beside hiding this thing behind a VPN (which I’m not prepared to do currently), is there anything else I’m overlooking?
Make sure your backups are solid and can’t be deleted or altered.
In addition to normal backups, something like zfs snapshots also help and make it easier to restore if needed.
I think I remember seeing a nextcloud plugin that detects mass changes to a lot of files (like ransomware would cause). Maybe something like that would help?
Also enforce good passwords.
Do you have anything exposed to the internet that also has access to either nextcloud or the server it’s running on? If so, lock that down as much as possible too.
Fail2ban or similar would help against brute force attacks.
The VM you’re running nextcloud on should be as isolated as you can comfortably make it. E.g. if you have a camera/iot vlan, don’t let the VM talk to it. Don’t let it initiate outbound connections to any of your devices, etc
You can’t entirely protect against zero day vulnerabilities, but you can do a lot to limit the risk and blast radius.