diff --git a/include/villas/hook.hpp b/include/villas/hook.hpp
index c288a0b17..6b60ebf27 100644
--- a/include/villas/hook.hpp
+++ b/include/villas/hook.hpp
@@ -45,10 +45,12 @@ class Hook {
 
 public:
 	enum class Flags {
-		BUILTIN = (1 << 0),   /**< Should we add this hook by default to every path?. */
-		PATH = (1 << 1),      /**< This hook type is used by paths. */
-		NODE_READ = (1 << 2), /**< This hook type is used by nodes. */
-		NODE_WRITE = (1 << 3) /**< This hook type is used by nodes. */
+		BUILTIN = (1 << 0),	/**< Should we add this hook by default to every path?. */
+		READ_ONLY = (1 << 1),	/**< The does not modify the sample contents */
+
+		PATH = (1 << 8),	/**< This hook type is used by paths. */
+		NODE_READ = (1 << 9),	/**< This hook type is used by nodes. */
+		NODE_WRITE = (1 << 10)	/**< This hook type is used by nodes. */
 	};
 
 	enum class Reason {
@@ -164,6 +166,11 @@ public:
 	{
 		return enabled;
 	}
+
+	bool isReadOnly() const
+	{
+		return flags & HookFlags::READ_ONLY;
+	}
 };
 
 class LimitHook : public Hook {
diff --git a/lib/hooks/decimate.cpp b/lib/hooks/decimate.cpp
index 6607e8c3b..b2a5e4457 100644
--- a/lib/hooks/decimate.cpp
+++ b/lib/hooks/decimate.cpp
@@ -69,7 +69,7 @@ Hook::Reason DecimateHook::process(sample *smp)
 /* Register hook */
 static char n[] = "decimate";
 static char d[] = "Downsamping by integer factor";
-static HookPlugin<DecimateHook, n, d, (int) Hook::Flags::NODE_READ | (int) Hook::Flags::NODE_WRITE | (int) Hook::Flags::PATH> p;
+static HookPlugin<DecimateHook, n, d, (int) Hook::Flags::READ_ONLY | (int) Hook::Flags::NODE_READ | (int) Hook::Flags::NODE_WRITE | (int) Hook::Flags::PATH> p;
 
 } /* namespace node */
 } /* namespace villas */
diff --git a/lib/hooks/drop.cpp b/lib/hooks/drop.cpp
index 4324e19eb..07c39aa02 100644
--- a/lib/hooks/drop.cpp
+++ b/lib/hooks/drop.cpp
@@ -98,7 +98,7 @@ public:
 /* Register hook */
 static char n[] = "drop";
 static char d[] = "Drop messages with reordered sequence numbers";
-static HookPlugin<DropHook, n, d, (int) Hook::Flags::BUILTIN | (int) Hook::Flags::NODE_READ, 3> p;
+static HookPlugin<DropHook, n, d, (int) Hook::Flags::READ_ONLY | (int) Hook::Flags::BUILTIN | (int) Hook::Flags::NODE_READ, 3> p;
 
 } /* namespace node */
 } /* namespace villas */
diff --git a/lib/hooks/dump.cpp b/lib/hooks/dump.cpp
index b4a780c6c..8bc2232ed 100644
--- a/lib/hooks/dump.cpp
+++ b/lib/hooks/dump.cpp
@@ -50,7 +50,7 @@ public:
 /* Register hook */
 static char n[] = "dump";
 static char d[] = "Dump data to stdout";
-static HookPlugin<DumpHook, n, d, (int) Hook::Flags::NODE_READ | (int) Hook::Flags::NODE_WRITE | (int) Hook::Flags::PATH, 1> p;
+static HookPlugin<DumpHook, n, d, (int) Hook::Flags::READ_ONLY | (int) Hook::Flags::NODE_READ | (int) Hook::Flags::NODE_WRITE | (int) Hook::Flags::PATH, 1> p;
 
 } /* namespace node */
 } /* namespace villas */
diff --git a/lib/hooks/gate.cpp b/lib/hooks/gate.cpp
index 5303f33eb..c8e763470 100644
--- a/lib/hooks/gate.cpp
+++ b/lib/hooks/gate.cpp
@@ -200,7 +200,7 @@ public:
 /* Register hook */
 static char n[] = "gate";
 static char d[] = "Skip samples only if an enable signal is under a specified threshold";
-static HookPlugin<GateHook, n, d, (int) Hook::Flags::NODE_READ | (int) Hook::Flags::PATH> p;
+static HookPlugin<GateHook, n, d, (int) Hook::Flags::READ_ONLY | (int) Hook::Flags::NODE_READ | (int) Hook::Flags::PATH> p;
 
 } /* namespace node */
 } /* namespace villas */
diff --git a/lib/hooks/jitter_calc.cpp b/lib/hooks/jitter_calc.cpp
index edf67274f..2f89ae276 100644
--- a/lib/hooks/jitter_calc.cpp
+++ b/lib/hooks/jitter_calc.cpp
@@ -114,7 +114,7 @@ public:
 /* Register hook */
 static char n[] = "jitter_calc";
 static char d[] = "Calc jitter, mean and variance of GPS vs NTP TS";
-static HookPlugin<JitterCalcHook, n, d, (int) Hook::Flags::NODE_READ | (int) Hook::Flags::PATH, 0> p;
+static HookPlugin<JitterCalcHook, n, d, (int) Hook::Flags::READ_ONLY | (int) Hook::Flags::NODE_READ | (int) Hook::Flags::PATH, 0> p;
 
 } /* namespace node */
 } /* namespace villas */
diff --git a/lib/hooks/limit_rate.cpp b/lib/hooks/limit_rate.cpp
index 1a05ec368..a18f04cfd 100644
--- a/lib/hooks/limit_rate.cpp
+++ b/lib/hooks/limit_rate.cpp
@@ -98,7 +98,7 @@ Hook::Reason LimitRateHook::process(sample *smp)
 /* Register hook */
 static char n[] = "limit_rate";
 static char d[] = "Limit sending rate";
-static HookPlugin<LimitRateHook, n, d, (int) Hook::Flags::NODE_READ | (int) Hook::Flags::NODE_WRITE | (int) Hook::Flags::PATH> p;
+static HookPlugin<LimitRateHook, n, d, (int) Hook::Flags::READ_ONLY | (int) Hook::Flags::NODE_READ | (int) Hook::Flags::NODE_WRITE | (int) Hook::Flags::PATH> p;
 
 } /* namespace node */
 } /* namespace villas */
diff --git a/lib/hooks/print.cpp b/lib/hooks/print.cpp
index c72cf402a..f651e99c5 100644
--- a/lib/hooks/print.cpp
+++ b/lib/hooks/print.cpp
@@ -138,7 +138,7 @@ public:
 /* Register hook */
 static char n[] = "print";
 static char d[] = "Print the message to stdout";
-static HookPlugin<PrintHook, n, d, (int) Hook::Flags::NODE_READ | (int) Hook::Flags::NODE_WRITE | (int) Hook::Flags::PATH> p;
+static HookPlugin<PrintHook, n, d, (int) Hook::Flags::READ_ONLY | (int) Hook::Flags::NODE_READ | (int) Hook::Flags::NODE_WRITE | (int) Hook::Flags::PATH> p;
 
 } /* namespace node */
 } /* namespace villas */
diff --git a/lib/hooks/skip_first.cpp b/lib/hooks/skip_first.cpp
index f055514f4..5977ea340 100644
--- a/lib/hooks/skip_first.cpp
+++ b/lib/hooks/skip_first.cpp
@@ -143,7 +143,7 @@ public:
 /* Register hook */
 static char n[] = "skip_first";
 static char d[] = "Skip the first samples";
-static HookPlugin<SkipFirstHook, n, d, (int) Hook::Flags::NODE_READ | (int) Hook::Flags::NODE_WRITE | (int) Hook::Flags::PATH> p;
+static HookPlugin<SkipFirstHook, n, d, (int) Hook::Flags::READ_ONLY | (int) Hook::Flags::NODE_READ | (int) Hook::Flags::NODE_WRITE | (int) Hook::Flags::PATH> p;
 
 } /* namespace node */
 } /* namespace villas */
diff --git a/lib/hooks/stats.cpp b/lib/hooks/stats.cpp
index 9d4799ecf..702dda60b 100644
--- a/lib/hooks/stats.cpp
+++ b/lib/hooks/stats.cpp
@@ -279,7 +279,7 @@ Hook::Reason StatsReadHook::process(sample *smp)
 /* Register hook */
 static char n[] = "stats";
 static char d[] = "Collect statistics for the current node";
-static HookPlugin<StatsHook, n, d, (int) Hook::Flags::NODE_READ> p;
+static HookPlugin<StatsHook, n, d, (int) Hook::Flags::READ_ONLY | (int) Hook::Flags::NODE_READ> p;
 
 } /* namespace node */
 } /* namespace villas */