  Infiltration of diffusing particles from one material to another where the
diffusion mechanism is either normal or anomalous is a widely observed
phenomena. When the diffusion is anomalous we find interesting behaviors:
diffusion may lead to an averaged net drift <x> from one material to another
even if all particles eventually flow in the opposite direction, or may lead to
a flow without drift. Starting with an underlying continuous time random walk
model we solve diffusion equations describing this problem. Similar drift
against flow is found in the quenched trap model. We argue that such a behavior
is a general feature of diffusion in disordered systems.
