Setting up Fail2ban with Overseerr (#739)

Co-authored-by: TheCatLady <52870424+TheCatLady@users.noreply.github.com>
Co-authored-by: Jakob Ankarhem <jakob.ankarhem@outlook.com>

docs/SUMMARY.md

@@ -18,4 +18,5 @@
 
 ## Extending Overseerr
 
-- [Reverse Proxy Examples](extending-overseerr/reverse-proxy-examples.md)
+* [Reverse Proxy Examples](extending-overseerr/reverse-proxy-examples.md)
+* [Fail2ban Filter](extending-overseerr/fail2ban.md)

docs/extending-overseerr/fail2ban.md

@@ -0,0 +1,14 @@
+# Fail2ban Filter
+
+{% hint style="warning" %}
+If you are running Overseerr behind a reverse proxy, make sure that the `PROXY` environment variable is set to `yes`.
+{% endhint %}
+
+To use Fail2ban with Overseerr, create a new file named `overseerr.local` in your Fail2ban `filter.d` directory with the following filter definition:
+
+```
+[Definition]
+failregex = .*\[info\]\[Auth\]\: Failed login attempt.*"ip":"<HOST>"
+```
+
+You can then add a jail using this filter in `jail.local`.  Please see the [Fail2ban documetation](https://www.fail2ban.org/wiki/index.php/MANUAL_0_8#Jails) for details on how to configure the jail.