  We investigate the properties of the background gauge field configurations
that act as disorder for the Anderson localization mechanism in the Dirac
spectrum of QCD at high temperatures. We compute the eigenmodes of the M\"obius
domain-wall fermion operator on configurations generated for the $SU(3)$ gauge
theory with two flavors of fermions, in the temperature range $[0.9,1.9]T_c$.
We identify the source of localization of the eigenmodes with gauge
configurations that are self-dual and support negative fluctuations of the
Polyakov loop $P_L$, in the high temperature sea of $P_L\sim 1$. The dependence
of these observations on the boundary conditions of the valence operator is
studied. We also investigate the spatial overlap of the left-handed and
right-handed projected eigenmodes in correlation with the localization and the
corresponding eigenvalue. We discuss an interpretation of the results in terms
of monopole-instanton structures.
