  Many Machine Learning models are vulnerable to adversarial attacks: There
exist methodologies that add a small (imperceptible) perturbation to an input
such that the model comes up with a wrong prediction. Better understanding of
such attacks is crucial in particular for models used in security-critical
domains, such as monitoring of water distribution networks, in order to devise
counter-measures enhancing model robustness and trustworthiness.
  We propose a taxonomy for adversarial attacks against machine learning based
leakage detectors in water distribution networks. Following up on this, we
focus on a particular type of attack: an adversary searching the least
sensitive point, that is, the location in the water network where the largest
possible undetected leak could occur. Based on a mathematical formalization of
the least sensitive point problem, we use three different algorithmic
approaches to find a solution. Results are evaluated on two benchmark water
distribution networks.
