  The search for a Standard Model Higgs boson with the $H\to WW^\ast\to
\ell\ell + E_{\rm T}^{\rm miss}$ decay and the application of a full-jet veto
yields a strong sensitivity in the mass range $130<m_H<200$ GeV. One of the
residual backgrounds is related to processes involving top quarks. A method for
the extraction of top backgrounds is evaluated at the parton and hadronic
levels based on the data-driven extraction of the jet veto survival
probability. The uncertainty of the proposed method is about 15%.
