How to secure your VPS with Fail2ban

When you configure a new server Fail2ban is a must-have tool to secure your VPS.

Fail2Ban scans log files and bans IPs that show the malicious signs (e.g. too many password failures, seeking for exploits, etc..). This tool update your firewall rules to reject the IP addresses for a specified amount of time, although any arbitrary other action (e.g. sending an email) could also be configured.

How to install

Centos

• Update the system, install EPEL repository and Fail2Ban:

    yum update && yum install epel-release
    yum install fail2ban

Debian

• Update the system and install Fail2Ban:

  apt-get update && apt-get upgrade -y
  sudo apt-get install fail2ban

Configure

Fail2ban reads .confconfiguration files first, then .local files override any settings. So the best way is edit the local configuration to override the defailt settings.

• Create a new local config file starting from the default one:
  cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local

• If using CentOS change the backend option in jail.local from auto to systemd. This is not necessary on Debian:

  [Default]
  # Available options are "pyinotify", "gamin", "polling", "systemd" and "auto".
  backend = systemd

• The most useful settings you can configure are:

  [DEFAULT]
  # "bantime" is the number of seconds that a host is banned.
  bantime = 10m
  # "maxretry" is the number of failures before a host get banned.
  maxretry = 5
  # "bantime.increment" allows to use database for searching of previously banned ip's to increase a
  # default ban time using special formula, default it is banTime * 1, 2, 4, 8, 16, 32...
  bantime.increment = false
  
  [sshd] 
  enabled = true
  # ssh port
  port = ssh
  

Running Fail2Ban service

Centos

systemctl enable fail2ban
systemctl start fail2ban

Debian

service fail2ban restart

Check the Fail2Ban Status

To check the status of the Fail2Ban jails:

fail2ban-client status

The result should be like this:

Status
|- Number of jail: 1
`- Jail list: sshd

If you want to see banned IPs in sshd jail:

fail2ban-client status sshd

Ban/Unban manually an IP address

In order to add/remove an IP address from the banned list use the following commands replacing IPADDRESS with the IP which needs unbanning, and the name “sshd” with name of the jail (in this case the “sshd” jail that we configured above):

fail2ban-client set sshd banip IPADDRESS
fail2ban-client set sshd unbanip IPADDRESS

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