CentOS 7.x fail2ban

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To configure fail2ban on CentOS 7.x use:

1. Install fail2ban using

   yum -y install epel-release
   yum -y install fail2ban

2. Create a local copy of configuration files for local modifications. We should not modify .conf files directly as they would get overwritten during package upgrades

   cp /etc/fail2ban/fail2ban.conf /etc/fail2ban/fail2ban.local
   cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local

3. Edit /etc/fail2ban/jail.local to enable jail for sshd

   [sshd]
   enabled = true

4. Start and enable fail2ban on system boot

   systemctl start fail2ban
   systemctl enable fail2ban

5. Ensure that firewalld is enabled as that is required by fail2ban using CentOS 7.x Basic firewalld configuration
6. Verify that fail2ban is running with at least 1 jail and that jail has one or more blocked IPs

   fail2ban-client status
   fail2ban-client status sshd

There is also older article on fail2ban at Fail2ban

In case of email server using postfix and dovecot add

   enabled=true

under '[dovecot]' and '[posfix-sasl]' also. This would then create three jails including sshd.

Refer:

• https://linode.com/docs/security/using-fail2ban-for-security/

Whitelist IPs

If the office public IPs are getting blacklisted due to wrong password in any application (eg thunderbird) by any user which is causing inconvinience for entire office then we can whitelist such public or private LAN IPs using:

ignoreip = 127.0.0.1 192.168.1.0/24 8.8.8.8

Refer:

• https://www.fail2ban.org/wiki/index.php/Whitelist

Since we have created jail.local file we should do this change in jail.local file and reload fail2ban.

Rate limiting using fail2ban

There is article on rate limiting connections to apache via fail2ban at Rocky_9.x_Rate_limiting_connections_to_apache#Rate_limiting_connections_via_fail2ban

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