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.
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
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 = email@example.com destemail = root action = %(action_mwl)s [sshd] enabled = true
Default time in seconds to ban the possible intruder. Common values are 3600 (1 hour) or 86400 (1 day).
Default "sender" email address when sending mail notifications of Fail2ban actions.
Destination email address for mail notifications.
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.
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.
This installs /etc/fail2ban/jail.d/00-firewalld.conf containing:
[DEFAULT] banaction = firewallcmd-ipset
Which configures fail2ban to block hosts via firewalld.
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