Protecting Proxmox web interface with fail2ban

apt install fail2ban

Create, if does not exist, the file jail.local (settings in this file takes precedence over identical settings of jail.conf. Use jail.conf as a template, copying and enabling into jail.local what you are interested in. Note that jail.conf could be overwritten by fail2ban package updates, jail.local will not)

The following configuration works, unchanged, for Proxmox VE > 3.x (last test with 7.1)

Add the following string to the end of this file /etc/fail2ban/jail.local :

[proxmox]
enabled = true
port = https,http,8006
filter = proxmox
logpath = /var/log/daemon.log
maxretry = 3
# 1 hour
bantime = 3600

Create the file /etc/fail2ban/filter.d/proxmox.conf :

[Definition]
failregex = pvedaemon\[.*authentication failure; rhost=<HOST> user=.* msg=.*
ignoreregex =

You can test your configuration trying to GUI login with a wrong password or user, and then issue the command :

fail2ban-regex /var/log/daemon.log /etc/fail2ban/filter.d/proxmox.conf

You should have *at least* a "Failregex: 1 total" at the top of the "Results" section (and "1 matched" at the bottom)

Restart fail2ban:

systemctl restart fail2ban