  We consider two-loop leading and next-to-leading logarithmic virtual
corrections to arbitrary processes with external massless fermions in the
electroweak Standard Model at energies well above the electroweak scale. Using
the sector-decomposition method and alternatively the strategy of regions we
calculate the mass singularities that arise as logarithms of Q^2/MW^2, where Q
is the energy scale of the considered process, and 1/\epsilon poles in
D=4-2\epsilon dimensions, to one- and two-loop next-to-leading logarithmic
accuracy. The derivations are performed within the complete electroweak theory
with spontaneous symmetry breaking. Our results indicate a close analogy
between the form of two-loop electroweak logarithmic corrections and the
singular structure of scattering amplitudes in massless QCD. We find agreement
with the resummation prescriptions that have been proposed in the literature
based on a symmetric SU(2) \times U(1) theory matched with QED at the
electroweak scale and provide new next-to-leading contributions proportional to
ln(MZ^2/MW^2).
