Fail2ban is an open source free intrusion prevention framework developed in python programming language. Fail2ban operates by monitoring log files such as /var/log/pwdfail, /var/log/auth.log, /var/log/secure etc. and bans the IP address after too many password failure attempts. It used to update iptable firewall rules to reject the IP address for a specified amount of time.
After making any changes to the fail2ban config, always be sure to restart Fail2Ban:
You can see the rules that fail2ban puts in effect within the IP table:
Step One—Install Fail2Ban
rpm -Uvh http://dl.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpmFollow up by installing fail2ban:
yum install fail2banStep Two—Copy the Configuration File
The default fail2ban configuration file is location at
/etc/fail2ban/jail.conf. The configuration work should not be done in
that file, however, and we should instead make a local copy of it.
cp /etc/fail2ban/jail.conf /etc/fail2ban/jail.local
After the file is copied, you can make all of your changes within the
new jail.local file. Many of possible services that may need protection
are in the file already. Each is located in its own section, configured
and turned off.
Step Three—Configure defaults in Jail.Local
Open up the the new fail2ban configuration file:
vi /etc/fail2ban/jail.local
The first section of defaults covers the basic rules that fail2ban will
follow. If you want to set up more nuanced protection for your virtual
private server, you can customize the details in each section.
You can see the default section below.[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.
ignoreip = 127.0.0.1
# "bantime" is the number of seconds that a host is banned.
bantime = 3600
# 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.
maxretry = 3
Write your personal IP address into the ignoreip line. You can
separate each address with a space. IgnoreIP allows you white list
certain IP addresses and make sure that they are not locked out from
your VPS. Including your address will guarantee that you do not
accidentally ban yourself from your own virtual private server.
The next step is to decide on a bantime, the number of seconds
that a host would be blocked from the server if they are found to be in
violation of any of the rules. This is especially useful in the case of
bots, that once banned, will simply move on to the next target. The
default is set for 10 minutes—you may raise this to an hour (or higher)
if you like.
Maxretry is the amount of incorrect login attempts that a host may have before they get banned for the length of the ban time.
Findtime refers to the amount of time that a host has to log in.
The default setting is 10 minutes; this means that if a host attempts,
and fails, to log in more than the maxretry number of times in the
designated 10 minutes, they will be banned.
Step Four (Optional)—Configure the ssh-iptables Section in Jail.Local
The SSH details section is just a little further down in the config, and it is already set up and turned on. Although you should not be required to make to make any changes within this section, you can find the details about each line below.
[ssh-iptables]
enabled = true
filter = sshd
action = iptables[name=SSH, port=ssh, protocol=tcp]
sendmail-whois[name=SSH, dest=root, sender=fail2ban@example.com]
logpath = /var/log/secure
maxretry = 5
Enabled simply refers to the fact that SSH protection is on. You can turn it off with the word "false".
The filter, set by default to sshd, refers to the config file
containing the rules that fail2banuses to find matches. The name is a
shortened version of the file extension. For example, sshd refers to the
/etc/fail2ban/filter.d/sshd.conf.
Action describes the steps that fail2ban will take to ban a
matching IP address. Just like the filter entry, each action refers to a
file within the action.d directory. The default ban action, "iptables"
can be found at /etc/fail2ban/action.d/iptables.conf .
In the "iptables" details, you can customize fail2ban further. For
example, if you are using a non-standard port, you can change the port
number within the brackets to match, making the line look more like
this:
eg. iptables[name=SSH, port=30000, protocol=tcp]
You can change the protocol from TCP to UDP in this line as well, depending on which one you want fail2ban to monitor.
If you have a mail server set up on your virtual private server,
Fail2Ban can email you when it bans an IP address. In the default case,
the sendmail-whois refers to the actions located at
/etc/fail2ban/action.d/sendmail-whois.conf.
log path refers to the log location that fail2ban will track.
The max retry line within the SSH section has the same
definition as the default option. However, if you have enabled multiple
services and want to have specific values for each one, you can set the
new max retry amount for SSH here.Step Five—Restart Fail2Ban
After making any changes to the fail2ban config, always be sure to restart Fail2Ban:
sudo service fail2ban restartYou can see the rules that fail2ban puts in effect within the IP table:
iptables -L
