  Recently the IceCube collaboration has reported the observation of 28
contained events with a visible energy in the interval between 60 TeV and 1.5
PeV, and has argued that this detection is evidence, with a statistical
significance of more than four standard deviations, for the existence of an
astrophysical neutrino flux that accounts for a large fraction of the events.
In this work we analyze the arguments that allow to identify a component of
astrophysical origin in the high energy neutrino flux separating it from
atmospheric neutrinos. An astrophysical origin for a large fraction of the
IceCube contained events is the simplest and most natural explanation of the
data but, conservatively, an atmospheric origin cannot yet be entirely ruled
out. This ambiguity should soon be resolved.
