fail2ban block ip/network range (ipv4 only)

A python script that group IPs into network range, to block attacks from a network range address, from CIDR /23 up to /31.

Please be carefull to not block youself!

Installation

Script

• Copy script into directory /usr/bin/
• Make it executable by chmod a+x /usr/bin/fail2ban-block-ip-range.py

Regular execution

By cron

Alternative 1: extension of /etc/crontab

Add following extension to /etc/crontab

*/5 * * * * /usr/bin/fail2ban-block-ip-range.py

Alternative 2: sniplet in /etc/cron.d/fail2ban-block-ip-range

*/5 * * * * root /usr/bin/fail2ban-block-ip-range.py

Common:

• watch output of cron log (usually /var/log/cron)
• watch e-mails sent to root (in case of script send something to stdout/stderr)

By systemd/timer

• Store unit files into /usr/lib/systemd/system/
• Reload systemd with systemctl daemon-reload
• Run a one-shot for testinger with systemctl enable fail2ban-block-ip-range.timer
• Check journald with journalctl -b 0 -u fail2ban-block-ip-range.service
• Enable the timer with systemctl enable fail2ban-block-ip-range.timer
• Check journald with journalctl -b 0 -u fail2ban-block-ip-range.timer

Note: output of the script to stdout/stderr will be logged to journald

SELinux

Active SELinux can prevent the script from being executed by cron/systemd!

Solution: toggle SELinux to run in permissive mode and create from all the logged events then a policy extension.

Example:

Count and IPs found at last 1k lines of fail2ban.log

    108 postfix-sasl 45.142.120.135
    107 postfix-sasl 45.142.120.62
    105 postfix-sasl 45.142.120.99
    105 postfix-sasl 45.142.120.93
    105 postfix-sasl 45.142.120.192
    104 postfix-sasl 45.142.120.87
    104 postfix-sasl 45.142.120.60
    104 postfix-sasl 45.142.120.209
    104 postfix-sasl 45.142.120.200
    104 postfix-sasl 45.142.120.133
    103 postfix-sasl 45.142.120.180
    103 postfix-sasl 45.142.120.149
    102 postfix-sasl 45.142.120.59
    100 postfix-sasl 45.142.120.215
     78 postfix-sasl 45.142.120.57
     78 postfix-sasl 45.142.120.11
     77 postfix-sasl 45.142.120.82
     77 postfix-sasl 45.142.120.20
     76 postfix-sasl 45.142.120.63
     76 postfix-sasl 45.142.120.34
     76 postfix-sasl 45.142.120.138
     73 postfix-sasl 45.142.120.65
      6 apache-auth 45.150.206.113
      3 postfix-sasl 123.30.50.91
      2 sshd 5.188.206.204
      2 apache-auth 45.150.206.119
      2 apache-auth 45.150.206.115
      2 apache-auth 45.150.206.114
      1 sshd 51.210.127.200

Resulting blocked IP and IP Ranges (above 10 events):

fail2ban-client set postfix-sasl banip 45.142.120.0/24
fail2ban-client set apache-auth banip 45.150.206.112/29