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Basic description of what will be done and what is expected.

1. You need the EPEL repo and Fail2ban:

yum install fail2ban

2. Edit the jail.conf to configure it for your needs:

The configuration file is located in: /etc/fail2ban/jail.conf You can use a text editor such as vi or nano to edit the file. Comments have been added to better help you understand the options.

# Fail2Ban configuration file
#
# Author: Cyril Jaquier
#
# $Revision: 747 $
#
# The DEFAULT allows a global definition of the options. They can be override
# in each jail afterwards.
[DEFAULT]
# "ignoreip" can be an IP address, a CIDR mask or a DNS host. Fail2ban will not
# ban a host which matches an address in this list. Several addresses can be
# defined using space separator.<strong>ignoreip = 127.0.0.1</strong>
<em>#Add another ignoreip directive here and put your ip if it doesn't change. #This will prevent you from banning yourself by accident.</em>
# "bantime" is the number of seconds that a host is banned.
bantime  = 600
<strong>bantime = 99999999999999999999999999999999999999999999999</strong>
<em>#This effectively sets the ban infintely. Adjust to your needs. The default is 10 minutes, or 600 seconds.</em>
# A host is banned if it has generated "maxretry" during the last "findtime"
# seconds.
findtime  = 600
# "maxretry" is the number of failures before a host get banned.
<strong>maxretry = 3</strong>
<em>It's ok to leave this at 3, for more security or if you use keys only, set it to 1. A setting of one will ban anyone who attempts to login without a key.</em>
# "backend" specifies the backend used to get files modification. Available
# options are "gamin", "polling" and "auto". This option can be overridden in
# each jail too (use "gamin" for a jail and "polling" for another).
#
# gamin:   requires Gamin (a file alteration monitor) to be installed. If Gamin
#          is not installed, Fail2ban will use polling.
# polling: uses a polling algorithm which does not require external libraries.
# auto:    will choose Gamin if available and polling otherwise.
backend = auto
# This jail corresponds to the standard configuration in Fail2ban 0.6.
# The mail-whois action send a notification e-mail with a whois request
# in the body.
<strong>[ssh-iptables] enabled = true filter = sshd action = iptables[name=SSH, port=ssh, protocol=tcp] sendmail-whois[name=SSH, [email protected], [email protected]] logpath = /var/log/secure maxretry = 5</strong>
<em>#This is the most popular/necessary chain, set your email destination and sender here. #This will notify you when a user is added/banned in this chain. dest= is your email #address, sender= is the address the email comes from for filtering purposes.</em>
[proftpd-iptables]
enabled  = false
filter   = proftpd
action   = iptables[name=ProFTPD, port=ftp, protocol=tcp]
           sendmail-whois[name=ProFTPD, [email protected]]
logpath  = /var/log/proftpd/proftpd.log
maxretry = 6
# This jail forces the backend to "polling".
[sasl-iptables]
enabled  = false
filter   = sasl
backend  = polling
action   = iptables[name=sasl, port=smtp, protocol=tcp]
           sendmail-whois[name=sasl, [email protected]]
logpath  = /var/log/mail.log
# Here we use TCP-Wrappers instead of Netfilter/Iptables. "ignoreregex" is
# used to avoid banning the user "myuser".
[ssh-tcpwrapper]
enabled     = false
filter      = sshd
action      = hostsdeny
              sendmail-whois[name=SSH, [email protected]]
ignoreregex = for myuser from
logpath     = /var/log/sshd.log
# This jail demonstrates the use of wildcards in "logpath".
# Moreover, it is possible to give other files on a new line.
[apache-tcpwrapper]
enabled  = falsefilter	 = apache-auth
action   = hostsdenylogpath  = /var/log/apache*/*error.log
           /home/www/myhomepage/error.log
maxretry = 6
# The hosts.deny path can be defined with the "file" argument if it is
# not in /etc.
[postfix-tcpwrapper]
enabled  = false
filter   = postfix
action   = hostsdeny[file=/not/a/standard/path/hosts.deny]
           sendmail[name=Postfix, [email protected]]
logpath  = /var/log/postfix.log
bantime  = 300
# Do not ban anybody. Just report information about the remote host.
# A notification is sent at most every 600 seconds (bantime).
[vsftpd-notification]
enabled  = false
filter   = vsftpd
action   = sendmail-whois[name=VSFTPD, [email protected]]
logpath  = /var/log/vsftpd.log
maxretry = 5
bantime  = 1800
# Same as above but with banning the IP address.
[vsftpd-iptables]
enabled  = false
filter   = vsftpd
action   = iptables[name=VSFTPD, port=ftp, protocol=tcp]
           sendmail-whois[name=VSFTPD, [email protected]]
logpath  = /var/log/vsftpd.log
maxretry = 5
bantime  = 1800
# Ban hosts which agent identifies spammer robots crawling the web
# for email addresses. The mail outputs are buffered.
[apache-badbots]
enabled  = false
filter   = apache-badbots
action   = iptables-multiport[name=BadBots, port="http,https"]
           sendmail-buffered[name=BadBots, lines=5, [email protected]]
logpath  = /var/www/*/logs/access_log
bantime  = 172800
maxretry = 1
# Use shorewall instead of iptables.
[apache-shorewall]
enabled  = false
filter   = apache-noscript
action   = shorewall
           sendmail[name=Postfix, [email protected]]
logpath  = /var/log/apache2/error_log
# Ban attackers that try to use PHP's URL-fopen() functionality
# through GET/POST variables. - Experimental, with more than a year
# of usage in production environments.
[php-url-fopen]
enabled = false
port    = http,https
filter  = php-url-fopen
logpath = /var/www/*/logs/access_log
maxretry = 1
# A simple PHP-fastcgi jail which works with lighttpd.
# If you run a lighttpd server, then you probably will
# find these kinds of messages in your error_log:
# ALERT – tried to register forbidden variable ‘GLOBALS’
# through GET variables (attacker '1.2.3.4', file '/var/www/default/htdocs/index.php')
# This jail would block the IP 1.2.3.4.
[lighttpd-fastcgi]
enabled = false
port    = http,https
filter  = lighttpd-fastcgi
# adapt the following two items as needed
logpath = /var/log/lighttpd/error.log
maxretry = 2
# This jail uses ipfw, the standard firewall on FreeBSD. The "ignoreip"
# option is overridden in this jail. Moreover, the action "mail-whois" defines
# the variable "name" which contains a comma using "". The characters '' are
# valid too.
[ssh-ipfw]
enabled  = false
filter   = sshd
action   = ipfw[localhost=192.168.0.1]
           sendmail-whois[name="SSH,IPFW", [email protected]]
logpath  = /var/log/auth.log
ignoreip = 168.192.0.1
# These jails block attacks against named (bind9). By default, logging is off
# with bind9 installation. You will need something like this:
#
# logging {
#     channel security_file {
#         file "/var/log/named/security.log" versions 3 size 30m;
#         severity dynamic;
#         print-time yes;
#     };
#     category security {
#         security_file;
#     };
# };
#
# in your named.conf to provide proper logging.
# This jail blocks UDP traffic for DNS requests.
[named-refused-udp]
enabled  = false
filter   = named-refused
action   = iptables-multiport[name=Named, port="domain,953", protocol=udp]
           sendmail-whois[name=Named, [email protected]]
logpath  = /var/log/named/security.log
ignoreip = 168.192.0.1
# This jail blocks TCP traffic for DNS requests.
[named-refused-tcp]
enabled  = false
filter   = named-refused
action   = iptables-multiport[name=Named, port="domain,953", protocol=tcp]
           sendmail-whois[name=Named, [email protected]]
logpath  = /var/log/named/security.log
ignoreip = 168.192.0.1

3. Set Fail2ban to start on boot and start the service right now:

chkconfig --level 23 fail2ban on && service fail2ban start

 

Troubleshooting / How To Test

Explanation troubleshooting basics and expectations.

Restart IPtables, Fail2ban and check the status of the Fail2ban install:

service iptables restart && service iptables status

Remove a ban from the Fail2ban SSH chain (change IP address):

iptables -D fail2ban-SSH -s 192.168.1.0 -j DROP
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How to: CentOS Virtualmin Fail2Ban
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