Minecraft wiki entry for Survival_in_an_infinite_desert, associated text: On your first or second day build a defensive system around your house. Dig two-block-deep trenches (or two-block high sand walls) in a square or ring around your house, at least 3 blocks away from your house walls. So for a 5x5 walled house, dig an 11x11 or 13x13 square ditch.