Fail2Ban Demystified: Custom Fail2Ban Actions

October 1, 2024 Reading time: 33 minutes

Fail2Ban is a powerful security tool that bridges your public-facing network services (ssh, mail server, web server, etc.) and your firewall. The Fail2Ban daemon constantly monitors your server logs, looking for troublemakers. When an intruder or suspicious activity is detected, it takes action! By default, Fail2Ban writes a temporary firewall rule that blocks the offender’s IP address on selected ports for a short period of time.

The real power in Fail2Ban, though, lies in its customizability. Using custom action scripts, admins can configure how Fail2Ban responds to threats, extending its abilities far beyond simply interfacing with the firewall. For example, you can define actions that will send an email or notification, write to a log file or database, invoke a web API, react differently in different contexts, and so on. The possibilities are unlimited!

This article explains how actions in Fail2Ban are defined and customized so that you can get the most out of Fail2Ban.

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