📖 ~1 min read
Table of contents
Symptom & Impact
Repeated attack attempts continue without automatic bans.
Environment & Reproduction
Frequently appears after log format/path changes or service migration.
Root Cause Analysis
Fail2ban watches an outdated or empty logfile and never matches patterns.
Quick Triage
Run `sudo fail2ban-client status` and inspect jail list plus ban counters.
Step-by-Step Diagnosis
Confirm `logpath` in jail config points to active auth/application log and test regex with current lines.
Solution – Primary Fix
Update jail `logpath`, reload fail2ban, and verify bans trigger on new failed attempts.
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Solution – Alternative Approaches
Enable systemd backend for journal-based matching when file logs are inconsistent.
Verification & Acceptance Criteria
New malicious attempts increase fail count and produce active bans.
Rollback Plan
Restore prior jail config if updated regex causes false positives.
Prevention & Hardening
Review jail mappings after logging stack or service changes.
Related Errors & Cross-Refs
Related to rsyslog/journald forwarding gaps and timezone mismatch in logs.
Related tutorial: View the step-by-step tutorial for debian-10.
View all debian-10 tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
Debian fail2ban and intrusion-prevention docs.
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