I just wall myself up inside with a gate and wait out the sieges. I also place two dogs outside the main entrance to catch kidnappers. Has the same effect without needing to mod the game or alter the settings.

Of course once I can build ballastas or make use of water/lava, I can set up winding paths with Dwarven Shotguns (basically using water pressure and garbage I can fire minecarts full of crap at high speeds) to obliterate trespassers.