  Beyond individually resolvable gravitational wave events such as binary black
hole and binary neutron star mergers, the superposition of many more weak
signals coming from a multitude of sources is expected to contribute to an
overall background, the so-called stochastic gravitational wave background. In
this review, we give an overview of possible detection methods in the search
for this background and provide a detailed review of the data-analysis
techniques, focusing primarily on current Earth-based interferometric
gravitational-wave detectors. In addition, various validation techniques aimed
at reinforcing the claim of a detection of such a background are discussed as
well. We conclude this review by listing some of the astrophysical and
cosmological implications resulting from current upper limits on the stochastic
background of gravitational waves.
