Fail2Ban

About

Fail2Ban is a small program which scans log files real-time and takes actions when hacking attempts are detected. More information about Fail2Ban can be found here

Protected services

Kolmisoft has implemented protection for these services:

• Asterisk - protects from brute-force registration attacks
• Apache - protects from scanning bots which try to access not existing address, for example http://YOUR_IP/PhpMyAdmin (correct end with Kolmisoft software is "phpmyadmin")
• SSH - protects from brute-force attacks.

Installation

Fail2Ban installation

Custom modifications

Remember to save backups for your custom modifications to Fail2Ban as automated installation/update/upgrade scripts can overwrite them.

If you have suggestions how Fail2Ban rules can be extended - please write to mindaugas.mardosas@kolmisoft.com

Modifying existing rules

All filters are enabled/disabled in /etc/fail2ban/jail.conf

To extend an existing filter please go to /etc/fail2ban/filter.d and open the required file. For example we will take /etc/fail2ban/filter.d/asterisk.conf:

bad patterns are specified at failregex variable as following:

failregex = NOTICE.* .*: Registration from '.*' failed for '<HOST>' - Wrong password
            NOTICE.* .*: Registration from '.*' failed for '<HOST>' - Peer is not supposed to register
            NOTICE.* .*: Registration from '.*' failed for '<HOST>' - No matching peer found
            NOTICE.* .*: Registration from '.*' failed for '<HOST>' - Username/auth name mismatch
            NOTICE.* .*: Registration from '.*' failed for '<HOST>' - Device does not match ACL
            NOTICE.* <HOST> failed to authenticate as '.*'$
            NOTICE.* .*: No registration for peer '.*' \(from <HOST>\)
            NOTICE.* .*: Host <HOST> failed MD5 authentication for '.*' (.*)
            NOTICE.* .*: Failed to authenticate user .*@<HOST>.*

you can add here your own.

Testing changes

You can test your new rules using fail2ban-regex tool as following:

fail2ban-regex /path/to/your/log/file/to/scan /etc/fail2ban/filter.d/asterisk.conf

This tool will show you how many matches were found and what regexp's were used.

Moving changes to production

Restart fail2ban:

/etc/init.d/fail2ban restart

See also

• Fail2Ban installation
• How to be secure using MOR