diff --git a/arakava-news/mu-plugins/arakava-comment-spam-guard.php b/arakava-news/mu-plugins/arakava-comment-spam-guard.php
new file mode 100644
index 000000000..72675074d
--- /dev/null
+++ b/arakava-news/mu-plugins/arakava-comment-spam-guard.php
@@ -0,0 +1,56 @@
+<?php
+/**
+ * Plugin Name: Arakava Comment Spam Guard (MU)
+ * Description: Markiert Kommentare mit blockierten Kurz-URL-Hosts als Spam (Standard: shorturl.fm). Erweiterbar per Filter arakava_spam_guard_blocked_hosts.
+ * Version: 1.0.0
+ * Author: Homelab / Arakava
+ */
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+/**
+ * @param string|int $approved Vorläufiger Freigabe-Status.
+ * @param array      $commentdata Rohdaten vor dem Speichern.
+ * @return string|int
+ */
+function arakava_spam_guard_pre_comment_approved( $approved, $commentdata ) {
+	if ( is_string( $approved ) && 'spam' === $approved ) {
+		return $approved;
+	}
+
+	$hosts = apply_filters(
+		'arakava_spam_guard_blocked_hosts',
+		array(
+			'shorturl.fm',
+		)
+	);
+
+	if ( empty( $hosts ) || ! is_array( $hosts ) ) {
+		return $approved;
+	}
+
+	$parts = array();
+	if ( ! empty( $commentdata['comment_content'] ) && is_string( $commentdata['comment_content'] ) ) {
+		$parts[] = $commentdata['comment_content'];
+	}
+	if ( ! empty( $commentdata['comment_author_url'] ) && is_string( $commentdata['comment_author_url'] ) ) {
+		$parts[] = $commentdata['comment_author_url'];
+	}
+
+	$blob = strtolower( implode( ' ', $parts ) );
+
+	foreach ( $hosts as $host ) {
+		$host = strtolower( trim( (string) $host ) );
+		if ( '' === $host ) {
+			continue;
+		}
+		if ( false !== strpos( $blob, $host ) ) {
+			return 'spam';
+		}
+	}
+
+	return $approved;
+}
+add_filter( 'pre_comment_approved', 'arakava_spam_guard_pre_comment_approved', 5, 2 );