How to block malicious web requests with BusinessPress

1. Make sure you follow the guide to setup fail2ban for BusinessPress
2. Edit /etc/fail2ban/action.d/iptables.conf, changing blocktype = REJECT --reject-with icmp-port-unreachable and blocktype = REJECT --reject-with icmp6-port-unreachable to blocktype = DROP. This is necessary to avoid multiple malicious requests to be sent over the already established TCP connection.
3. Create /etc/fail2ban/filter.d/waf.conf:

# Fail2Ban configuration file
#

[INCLUDES]

# Read common prefixes. If any customizations available -- read them from
# common.local
before = common.conf


[Definition]

_daemon = (?:wordpress|wp)

# Option:  failregex
# Notes.:  regex to match the password failures messages in the logfile. The
#          host must be matched by a group named "host". The tag "<HOST>" can
#          be used for standard IP/hostname matching and is only an alias for
#          (?:::f{4,6}:)?(?P<host>[\w\-.^_]+)
# Values:  TEXT
#
failregex = ^%(__prefix_line)sBusinessPress WAF .* from <HOST>$

# Option:  ignoreregex
# Notes.:  regex to ignore. If this regex matches, the line is ignored.
# Values:  TEXT
#
ignoreregex =

4. Create /etc/fail2ban/jail.d/waf.conf:

[waf]
enabled = true
filter = waf
logpath = /var/log/auth.log
port = http,https
backend = auto

maxretry = 1 ; ban after a single bad try
findtime = 1200
bantime = -1 ; bans the IP forever

ignoreip = 127.0.0.1 {your server IP here}

5. Run fail2ban-client -d to check configuration, fail2ban-client reload to reload it and fail2ban-client status to verify the new jail is added. You should now see waf in the list:

# fail2ban-client status
Status
|- Number of jail:  4
`- Jail list:   repeated, sshd, waf, wordpress

6. Use a VPN or some spare server to make a request to URL like https://your-site.com/.env.

7. Check fail2ban-client status waf to verify that the IP has been banned.