DUL Data Utility Labs

Regex - Private browser tool

Failregex Generator

Generate a Fail2ban-style failregex starter from a failed login log line and test the extracted host pattern.

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2026-05-04 12:41:03 Failed password for invalid user admin from 203.0.113.42 port 54421 ssh2

Failregex Generator

Private, browser-based, free to use.

What this tool helps you do

Generate a Fail2ban-style failregex starter from a failed login log line and test the extracted host pattern. Paste your data, run the tool, copy the result, and move on. The core workflow stays on one focused page.

Best use cases

  • Convert or clean data before importing it into spreadsheets, BI tools, databases, or internal apps.
  • Debug API payloads, logs, tokens, encodings, regular expressions, and text transformations.
  • Create lightweight examples for documentation, tests, tutorials, customer support, and team handoffs.

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Failregex Generator FAQ

Is this production-ready Fail2ban config?

It is a starter pattern. Test it with fail2ban-regex before production use.

What is <HOST>?

Fail2ban uses <HOST> as a placeholder for the offending IP or hostname.

Why is this useful?

It turns real log lines into a pattern you can refine instead of writing from scratch.