diff --git a/etc/fail2ban/filter.d/chasquid.conf b/etc/fail2ban/filter.d/chasquid.conf
new file mode 100644
index 0000000..b5c6e2e
--- /dev/null
+++ b/etc/fail2ban/filter.d/chasquid.conf
@@ -0,0 +1,11 @@
+# fail2ban filter config for chasquid SMTP server.
+[INCLUDES]
+before = common.conf
+
+[Definition]
+# Identify addresses that triggered an SMTP connection error.
+failregex = SMTP.Conn <ADDR>:\d+: error:
+
+[Init]
+journalmatch = _SYSTEMD_UNIT=chasquid.service
+