  We present a search strategy for both Dirac and Majorana sterile neutrinos
from the purely leptonic decays of $W^\pm \to e^\pm e^\pm \mu^\mp \nu$ and
$\mu^\pm \mu^\pm e^\mp \nu$ at the 14 TeV LHC. The discovery and exclusion
limits for sterile neutrinos are shown using both the Cut-and-Count (CC) and
Multi-Variate Analysis (MVA) methods. We also discriminate between Dirac and
Majorana sterile neutrinos by exploiting a set of kinematic observables which
differ between the Dirac and Majorana cases. We find that the MVA method,
compared to the more common CC method, can greatly enhance the discovery and
discrimination limits. Two benchmark points with sterile neutrino mass $m_N =
20$ GeV and 50 GeV are tested. For an integrated luminosity of 3000 ${\rm
fb}^{-1}$, sterile neutrinos can be found with $5 \sigma$ significance if
heavy-to-light neutrino mixings $|U_{Ne}|^2 \sim |U_{N\mu}|^2\sim 10^{-6}$,
while Majorana vs. Dirac discrimination can be reached if at least one of the
mixings is of order $10^{-5}$.
