 The great defence system of Gallifrey is a quantum forcefield known as the Transduction Barrier, a perfect defence shield preventing all matter and energy, even TARDISes, from passing through without authorisation.The Time Lords are further protected by phasing the entire region around Gallifrey into a temporal domain known as Inner Time, effectively separating the homeworld from interaction with the rest of the Universe.During the final hours of the Time War, the High Council of Gallifrey refer to defenses called 'Sky Trenches' which appear to be at least somewhat effective against invading Daleks and/or their ships, as seen in "The Day of the Doctor".