  In this work we present a comprehensive study of the spontaneous currents in
time-reversal symmetry breaking (TRSB) multi-component superconductors with
cubic crystalline symmetry. We argue, not limiting to cubic lattices, that
spontaneous current on certain high-symmetry surfaces can exist only if the
TRSB pairing simultaneously breaks a certain pair of mirror symmetries. This is
shown to have exact correspondence with the Gingzburg-Landau (GL) theory and is
verified by numerical Bogoliubov de-Gennes (BdG) calculations. In the course we
extend the BdG to include effects of gap anisotropy and surface disorder, both
of which could lead to a much suppressed current. The GL theory has been known
to describe well the spontaneous current. However, we highlight a special case
where it becomes less adequate, and show that a refined effective theory for
low temperatures is needed. These results could shed light on the phenomenology
of cubic superconductors such as U$_{1-x}$Th$_x$Be$_{13}$, the filled
skutterudites PrOs$_4$Sb$_{12}$, PrPt$_4$Ge$_{12}$ and related compounds.
