  We derive within a time-dependent scattering formalism expressions for both
the current through ac-driven nanoscale conductors and its fluctuations. The
results for the time-dependent current, its time average, and, above all, the
driven shot noise properties assume an explicit and serviceable form by
relating the propagator to a non-Hermitian Floquet theory. The driven noise
cannot be expressed in terms of transmission probabilities. The results are
valid for a driving of arbitrary strength and frequency. The connection with
commonly known approximation schemes such as the Tien-Gordon approach or a
high-frequency approximation is elucidated together with a discussion of the
corresponding validity regimes. Within this formalism, we study the coherent
suppression of current and noise caused by properly chosen electromagnetic
fields.
