Industrial Control System (ICS) networks transmit control and monitoring data in critical environments such as smart grid. Cyber attacks on smart grid communication may cause fatal consequences on energy production, distribution, and eventually the lives of people. Since the attacks can be initiated from both the inside and outside of the network, traditional smart grid security tools like firewalls or Intrusion Detection Systems (IDS), which are typically deployed on the edge of the network, are not able to detect internal threats. For this reason, we also need to analyze behavior of internal ICS communication.