  On the level of an effective quark theory, we define confinement by the
absence of quark anti-quark thresholds in correlation functions. We then
propose a confining Nambu-Jona-Lasinio-type model. The confinement is
implemented in analogy to Anderson localization in condensed matter systems. We
study the model's phase structure as well as its behavior under extreme
conditions, i.e.\ high temperature and/or high density.
