In the AdS/CFT context, black holes are dual to ensembles of ``heavy'' CFT states whose conformal dimension scales as the central charge. The Strominger--Vafa black hole, which admits an AdS$_3 \times$ S$^3$ decoupling limit and a dual description in terms of a two-dimensional CFT, provides an excellent model to study. \par Among the dynamical quantities one can study, the four-point functions, with two heavy states and two light probes, provide a good observable to extract detailed informations from the black hole. In particular, late time behavior of the correlators is associated to information loss and generally it provides a powerful tools to study unitarity properties of the system.