Fail2ban scans log files for malicious patterns and automatically blocks offending IPs. Combined with external blocklists, it provides powerful protection.
What is Fail2ban?
Fail2ban monitors log files for patterns indicating malicious activity - failed logins, exploit attempts, or abuse. When thresholds are exceeded, it bans the offending IP.
It works with various services including SSH, web servers, mail servers, and custom applications.
How Fail2ban Works
- Monitor Logs - Fail2ban continuously reads specified log files
- Match Patterns - Regex patterns (filters) identify malicious activity
- Count Failures - Track failures per IP within a time window
- Execute Action - Ban IP via iptables, firewalld, or custom action when threshold exceeded
Integrating External Blocklists
Enhance Fail2ban with preemptive blocking from threat feeds:
Jail configuration example:
[fraudcache-blocklist]
enabled = true
banaction = iptables-multiport
protocol = tcp
chain = INPUT
Best Practices
- Tune Thresholds - Balance security (low threshold) with false positives (high threshold)
- Use Appropriate Ban Times - Short bans for accidental failures, long for repeat offenders
- Monitor Ban Lists - Regularly review banned IPs for patterns and false positives
Get IP Blocklists for Fail2ban
Download threat feeds to preemptively block known bad actors.