Fail2ban help our servers to prevent the brute force attacks scanning the log files to find fail authentication attempts. Software like hydra can attempt to login in service that require authentication like telnet, ssh, http, ftp, etc… trying with an user and password combination based in dictionary. If our password have a strong combination It’s very difficult to obtain the access with this method, but the attempts will generate unnecessary traffic.


With Fail2ban there are some terms to define for config files:

  • filter: is a regular expression with must match a pattern corresponding with a failure in log file.
  • action: Define various commands executed in different moments.
  • jail: a combination of one filter and action.

In this scenario I’ll configure Fail2ban with a SSH server filtering with iptables and a FTP server (vsftpd) filtered by TCP wrappers using the file /etc/hosts.deny.

1.- Install EPEL repository from:

# rpm -ivh

2.- Install Fail2Ban and postfix to mail notifications:

# yum install fail2ban postfix mailx

3.- Edit the main config file /etc/fail2ban/jail.conf:

# Fail2ban will not ban a host which matches an address in this list
ignoreip =
# "bantime" is the number of seconds that a host is banned.
bantime = 600
# A host is banned if it has generated "maxretry" during the last "findtime".
findtime = 600
# "maxretry" is the number of failures before a host get banned.
maxretry = 3
# "backend" specifies the backend used to get files modification.
backend = auto
enabled = true
filter = sshd
action = iptables[name=SSH, port=ssh, protocol=tcp]
sendmail-whois[name=SSH, dest=root, [email protected]]
logpath = /var/log/secure
maxretry = 5
enabled = true
filter = vsftpd
action = hostsdeny[file=/etc/hosts.deny]
sendmail-whois[name=VSFTPD, dest=root,
[email protected]]
logpath = /var/log/vsftpd.log
maxretry = 5
bantime = 1800

4.- Start the services:

# service postfix start
# chkconfig --levels 235 postfix on
# service fail2ban start
# chkconfig --levels 235 fail2ban on

5.- Test the jail configured:


  • See the iptables rules generated by Fail2ban after a brute force attack to SSH service:


  •  To unban an IP address banned by iptables run this:
# iptables -D fail2ban-SSH -s -j DROP
  • See the file /etc/hosts.deny after brute force attack in FTP server:


  • Mail notification from SSH attack:

Official page of Fail2ban project:

Preventing brute force attacks with Fail2ban
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