In this overview we discuss the prospects for a first detection of an isotropic gravitational wave background with earth-based interferometric detectors. Furthermore, we focus on how correlated noise sources could endanger such a detection with current generation of detectors. Finally, we project how correlated noise could significantly impede the potential of the future detector, the Einstein Telescope, in its search for an isotropic gravitational wave background. The triangular configuration of three (almost) co-located detectors, makes the Einstein Telescope especially prone to correlated noise sources.