  We use high-resolution Eulerian simulations to study the stability of cold
gas flows in a galaxy size dark matter halo (10^12 Msun) at redshift z=2. Our
simulations show that a cold stream penetrating a hot gaseous halo is stable
against thermal convection and Kelvin-Helmholtz instability. We then
investigate the effect of a satellite orbiting the main halo in the plane of
the stream. The satellite is able to perturb the stream and to inhibit cold gas
accretion towards the center of the halo for 0.5 Gyr. However, if the supply of
cold gas at large distances is kept constant, the cold stream is able to
re-establish itself after 0.3 Gyr. We conclude that cold streams are very
stable against a large variety of internal and external perturbations.
