The undoped three-orbital spin fermion model for the Fe-based superconductors is studied via Monte Carlo techniques in two-dimensional clusters. At low temperatures, the magnetic and one-particle spectral properties are in good agreement with neutron and photoemission experiments. Our most important results are the resistance vs. temperature curves that display all the features experimentally observed in BaFe$_2$As$_2$ detwinned single crystals (under uniaxial stress), including a low-temperature anisotropy between the two directions followed by a peak at the magnetic ordering temperature, here induced by short-range spin order and concomitant Fermi Surface orbital order.
