Fail2ban

Configure Fail2ban against a disposable service log and simulate repeated failed logins from a test address. Confirm the jail matches the right log lines, imposes a ban for the intended duration, and records the action. Then test legitimate failed logins and administrative access from trusted networks.

Keep a recovery route that does not depend on the banned service. Review IPv6, log rotation, and firewall backend behavior. A ban rule is useful only if it slows abuse without silently locking out real users or the operator.