Elastic waves in the presence of a damaged interface between two dissimilar elastic media is investigated in the three-dimensional case. The damaged is modeled as a stochastic distribution of equally sized circular cracks which is transformed into a spring boundary condition. First the scattering by a single circular interface crack between two dissimilar half-spaces is investigated and solved explicitly for normally incident waves in the low frequency limit. The transmission by a distribution of cracks is then determined and is transformed into a spring boundary condition, where effective spring stiffnesses are expressed in terms of elastic moduli and damage parameters. A comparison with previous results for a periodic distribution of cracks shows good agreement.