kernel: [UFW BLOCK] IN=eth0 OUT=

sudo nano /etc/fail2ban/filter.d/ufw-block.conf

#add

[Definition]
failregex = ^.*?\[UFW BLOCK\].*?SRC=<HOST>
ignoreregex =

sudo nano /etc/fail2ban/jail.local

#add

[ufw-block]
enabled  = true
filter   = ufw-block
logpath  = /var/log/ufw.log
maxretry = 5
findtime = 600
bantime  = 3600
action   = iptables-allports[name=ufw-block]

#check

sudo systemctl restart fail2ban
sudo fail2ban-client status ufw-block

Status for the jail: ufw-block
|- Filter
|  |- Currently failed:	58
|  |- Total failed:	368
|  `- File list:	/var/log/ufw.log
`- Actions
   |- Currently banned:	60
   |- Total banned:	61
   `- Banned IP list: XXXXXXXXXXXXXXXXXXXX ;)