  We construct a real time current-conserving functional renormalization group
(RG) scheme on the Keldysh contour to study frequency-dependent transport and
noise through a quantum dot in the local moment regime. We find that the
current vertex develops a non-trivial non-local structure in time, governed by
a new set of RG equations. Solving these RG equations, we compute the complete
frequency and temperature-dependence of the noise spectrum. For voltages large
compared to the Kondo temperature, $eV \gg k_BT_K$, two sharp anti-resonances
are found in the noise spectrum at frequencies $\hbar \omega = \pm e V$, and
correspondingly, two peaks in the ac conductance through the dot.
