  We analyze and design a control strategy for nonlinear systems under
Denial-of-Service attacks. Based on an ISS-Lyapunov function analysis, we
provide a characterization of the maximal percentage of time during which
feedback information can be lost without resulting in the instability of the
system. Motivated by the presence of a digital channel we consider event-based
controllers for which a minimal inter-sampling time is explicitly
characterized.
