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Revision as of 21:21, 28 February 2015 by Dale (talk | contribs) (Configuration: fix path to sample config so it actually works)

Fail2ban is a service that monitors logfiles to detect potential intrusion attempts and places bans using a variety of methods. In Fedora 20, the default firewall service FirewallD can be used as a ban action.

Setup

First, install Fail2ban and requirements for utilizing FirewallD (This tutorial requires Fail2ban 0.9.0 or higher):

sudo yum install fail2ban ipset

If you wish to have Fail2ban send mail notifications, install these packages as well (sendmail can be used instead of postfix):

sudo yum install postfix whois fail2ban-sendmail

If you did not already have postfix (or sendmail) set up, you must enable the service:

sudo systemctl enable postfix
sudo systemctl start postfix

Configuration

Fail2ban is configured by the file /etc/fail2ban/jail.conf, but you should not modify this file directly. Instead, create a local configuration file at /etc/fail2ban/jail.d/local.conf. Here is an example local.conf that will send an email to root when IPs are banned:

[DEFAULT]
bantime = 3600
banaction = firewallcmd-ipset
backend = systemd
sender = fail2ban@example.com
destemail = root
action = %(action_mwl)s

[sshd]
enabled = true

bantime

Default time in seconds to ban the possible intruder. Common values are 3600 (1 hour) or 86400 (1 day).

banaction

Configures Fail2ban to use FirewallD as the default ban action.

backend

Configures Fail2ban to use SystemD to monitor logfiles. If you are not using SystemD for logging, you can leave out this option.

sender

Default "sender" email address when sending mail notifications of Fail2ban actions.

destemail

Destination email address for mail notifications.

action

Action to take when a possible intruder is detected. Default is %(action_)s which will only ban the IP. With %(action_mwl)s it will ban the IP and send a mail notification including whois data and log entries. See comments in /etc/fail2ban/jail.conf for more information.

Jails

By enabling the sshd jail, fail2ban will monitor ssh connection attempts for IPs to ban. There are many other jails you can enable as well, such as apache-auth to monitor the HTTPD error log for authentication failures, and jails for authentication to various FTP, IMAP, SMTP and database servers. See /etc/fail2ban/jail.conf for a full list of defined jails, or define your own.

Running the service

Once configured, start the service:

sudo systemctl start fail2ban

And enable it to run on system startup:

sudo systemctl enable fail2ban

Check the status:

systemctl status fail2ban

Check the log file:

sudo tail /var/log/fail2ban.log