  We present a detailed analysis of the radio synchrotron emission induced by
WIMP dark matter annihilations and decays in extragalactic halos. We compute
intensity, angular correlation, and source counts and discuss the impact on the
expected signals of dark matter clustering, as well as of other astrophysical
uncertainties as magnetic fields and spatial diffusion. Bounds on dark matter
microscopic properties are then derived, and, depending on the specific set of
assumptions, they are competitive with constraints from other indirect dark
matter searches. At GHz frequencies, dark matter sources can become a
significant fraction of the total number of sources with brightness below the
microJansky level. We show that, at this level of fluxes (which are within the
reach of the next-generation radio surveys), properties of the faint edge of
differential source counts, as well as angular correlation data, can become an
important probe for WIMPs.
