Fail2ban with FirewallD

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Fail2ban is a service that monitors logfiles to detect potential intrusion attempts and places bans using a variety of methods. In Fedora and EL7, the default firewall service FirewallD can be used as a ban action.

Contents

Setup

First, install Fail2ban and requirements for utilizing FirewallD:

sudo dnf install fail2ban

The fail2ban package is a meta-package that will bring in fail2ban-server (the main fail2ban component) as well as fail2ban-firewalld (which configures fail2ban to use firewalld) and fail2ban-sendmail (which allows fail2ban to send email notifications). If you do not want to install fail2ban-sendmail, you can install just fail2ban-firewalld.

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 primarily 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.local or /etc/fail2ban/jail.d/local.conf. Here is an example jail.local that will send an email to root when IPs are banned:

[DEFAULT]
bantime = 3600
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).

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.

fail2ban-firewalld

This installs /etc/fail2ban/jail.d/00-firewalld.conf containing:

[DEFAULT]
banaction = firewallcmd-ipset

Which configures fail2ban to block hosts via firewalld.

fail2ban-systemd

When trying to start fail2ban with systemd'd journald as the primary logging you may see this error

ERROR  No file(s) found for glob /var/log/secure
ERROR  Failed during configuration: Have not found any log file for sshd jail

To resolve this package installs /etc/fail2ban/jail.d/00-systemd.conf containing:

[DEFAULT]
backend=systemd

Which configures fail2ban to log via systemd's journald.

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