  For many coupled dynamical systems, the interaction is the outcome of the
measurement that each unit has of the others as e.g. in modern inverter-based
power grids, autonomous vehicular platoons or swarms of drones, or it is the
results of physical flows. Synchronization among all the components of these
systems is of primal importance to avoid failures. The overall operational
state of these systems therefore crucially depends on the correct and reliable
functioning of the individual elements as well as the information they transmit
through the network. Here, we investigate the effect of Byzantine attacks where
one unit does not behave as expected, but is controlled by an external
attacker. For such attacks, we assess the impact on the global collective
behavior of nonlinearly coupled phase oscillators. We relate the
synchronization error induced by the input signal to the properties of the
attacked node. This allows to anticipate the potential of an attacker and
identify which network components to secure.
