diff --git a/virtweb_backend/src/controllers/nwfilter_controller.rs b/virtweb_backend/src/controllers/nwfilter_controller.rs
index 8bda625..bdbbbcb 100644
--- a/virtweb_backend/src/controllers/nwfilter_controller.rs
+++ b/virtweb_backend/src/controllers/nwfilter_controller.rs
@@ -100,6 +100,13 @@ pub async fn update(
 
 /// Delete a network filter
 pub async fn delete(client: LibVirtReq, path: web::Path<NetworkFilterID>) -> HttpResult {
+    // Prevent deletion of default rules
+    let network = client.get_single_network_filter(path.uid).await?;
+    if constants::BUILTIN_NETWORK_FILTER_RULES.contains(&network.name.as_str()) {
+        return Ok(HttpResponse::ExpectationFailed()
+            .json("Builtin network filter rules shall not be deleted!"));
+    }
+
     client.delete_network_filter(path.uid).await?;
 
     Ok(HttpResponse::Ok().json("Network deleted"))