Update #6 - Fail2Ban Security Hardening - Longer Bans, Fewer Chances

After implementing a dynamic ignoreip rule using my DDNS hostname in Update #5, I proceeded to further harden my Fail2Ban configuration. The goal was to tighten lockout criteria and extend ban durations to reduce the risk of brute-force attacks on my VPS.

What I Changed

• Increased Ban Duration:
  Set bantime to 12h so attackers are kept out for a long stretch.

• Shortened Detection Window:
  Set findtime to 10m, limiting how far back Fail2Ban looks for failed attempts.

• Stricter Retry Limit:
  Set maxretry to 3, meaning three failed login attempts trigger a ban.

• Updated jail.local Configuration:

[DEFAULT]
ignoreip = 127.0.0.1 <dynamic-ip-from-ddns>
bantime = 12h
findtime = 10m
maxretry = 3

 Note: The <dynamic-ip-from-ddns> is automatically updated via a custom script that resolves my DDNS hostname and inserts the current IP.

Verification

To confirm the configuration was working as expected, I ran:

sudo fail2ban-client status sshd
sudo tail -f /var/log/fail2ban.log

This verified that failed attempts were being logged, and offenders were banned promptly after 3 failures.

Result

The system is now more secure, allowing fewer login attempts and keeping bad actors out longer. With dynamic DDNS-based whitelisting and aggressive jail parameters, my SSH service is much better protected going forward.