diff --git a/include/villas/hook.hpp b/include/villas/hook.hpp
index 6b60ebf27..59f688e5c 100644
--- a/include/villas/hook.hpp
+++ b/include/villas/hook.hpp
@@ -169,7 +169,7 @@ public:
 
 	bool isReadOnly() const
 	{
-		return flags & HookFlags::READ_ONLY;
+		return flags & (int) Flags::READ_ONLY;
 	}
 };
 
diff --git a/include/villas/hook_list.hpp b/include/villas/hook_list.hpp
index 89a718238..178d04773 100644
--- a/include/villas/hook_list.hpp
+++ b/include/villas/hook_list.hpp
@@ -76,3 +76,5 @@ void hook_list_stop(struct vlist *hs);
 struct vlist * hook_list_get_signals(struct vlist *hs);
 
 json_t * hook_list_to_json(struct vlist *hs);
+
+bool hook_list_is_read_only(struct vlist *hs);
diff --git a/include/villas/node_direction.h b/include/villas/node_direction.h
index 109b96081..303a1938a 100644
--- a/include/villas/node_direction.h
+++ b/include/villas/node_direction.h
@@ -53,8 +53,10 @@ struct vnode_direction {
 	 */
 	struct vpath *path;
 
-	int enabled;
-	int builtin;		/**< This node should use built-in hooks by default. */
+	bool enabled;		/**< This node direction is enabled. */
+	bool builtin_hooks;	/**< This node direction should use built-in hooks by default. */
+	bool read_only_hooks;	/**< The hooks of this node direction do not alter samples while processing them. */
+
 	unsigned vectorize;	/**< Number of messages to send / recv at once (scatter / gather) */
 
 	struct vlist hooks;	/**< List of read / write hooks (struct hook). */
diff --git a/lib/hook_list.cpp b/lib/hook_list.cpp
index db6824982..93dfe4604 100644
--- a/lib/hook_list.cpp
+++ b/lib/hook_list.cpp
@@ -105,25 +105,24 @@ void hook_list_prepare(struct vlist *hs, vlist *sigs, int m, struct vpath *p, st
 {
 	assert(hs->state == State::INITIALIZED);
 
-	if (!m)
-		goto skip_add;
-
 	/* Add internal hooks if they are not already in the list */
-	for (auto f : plugin::Registry::lookup<HookFactory>()) {
-		if ((f->getFlags() & m) == m) {
-			auto h = f->make(p, n);
+	if (m) {
+		for (auto f : plugin::Registry::lookup<HookFactory>()) {
+			if ((f->getFlags() & m) == m) {
+				auto h = f->make(p, n);
 
-			vlist_push(hs, h);
+				vlist_push(hs, h);
+			}
 		}
 	}
 
-skip_add:
 	/* Remove filters which are not enabled */
 	vlist_filter(hs, (dtor_cb_t) hook_is_enabled);
 
 	/* We sort the hooks according to their priority */
 	vlist_sort(hs, (cmp_cb_t) hook_cmp_priority);
 
+	/* Prepare signal list by passing is through all hooks */
 	for (size_t i = 0; i < vlist_length(hs); i++) {
 		Hook *h = (Hook *) vlist_at(hs, i);
 
@@ -222,3 +221,16 @@ json_t * hook_list_to_json(struct vlist *hs)
 
 	return json_hooks;
 }
+
+bool hook_list_is_read_only(struct vlist *hs)
+{
+	bool ret = true;
+
+	for (size_t i = 0; i < vlist_length(hs); i++) {
+		Hook *h = (Hook *) vlist_at_safe(hs, i);
+
+		ret &= h->isReadOnly();
+	}
+
+	return ret;
+}