Modern Networked Critical Infrastructures (NCI), involving cyber and physical systems, are exposed to intelligent cyber attacks targeting the stable operation of these systems. In order to ensure anomaly awareness, the observed data can be used in accordance with data mining techniques to develop Intrusion Detection Systems (IDS) or Anomaly Detection Systems (ADS). There is an increase in the volume of sensor data generated by both cyber and physical sensors, so there is a need to apply Big Data technologies for real-time analysis of large data sets. In this paper, we propose a clustering based approach for detecting cyber attacks that cause anomalies in NCI. Various clustering techniques are explored to choose the most suitable for clustering the time-series data features, thus classifying the states and potential cyber attacks to the physical system. The Hadoop implementation of MapReduce paradigm is used to provide a suitable processing environment for large datasets. A case study on a NCI consisting of multiple gas compressor stations is presented.