FlowGuard is based on the combination of IoT sensing infrastructure and Artificial Intelligence (Graph Neural Networks). Graph Neural Networks (GNNs) and IoT can play a significant role in preventing or mitigating cyber-attacks on public drinking water supply systems. GNNs can analyze large-scale graph data from the water system and identify any anomalous behavior or potential vulnerabilities in the network. GNNs and IoT can help with incident response by quickly identifying the source and extent of the attack, enabling targeted and efficient remediation. By responding quickly and effectively to a cyberattack, panic and potential harm to the general population can be avoided.