Some creatures have the ability to make incorporeal touch attacks. These attacks bypass solid objects, such as armor and shields, by passing through them. Incorporeal touch attacks work similarly to normal touch attacks except that they also ignore cover bonuses. Incorporeal touch attacks do not ignore armor bonuses granted by force effects, such as mage armor and bracers of armor.
So an incorporeal touch attack ignores the same things that a touch attack ignores, EXCEPT they also ignore cover and DO NOT ignore bonuses granted by force effects.
|Turin the Mad|
This is why I track all three AC types: touch AC, incorporeal touch AC and AC. spectral hand attacks incorporeal touch AC as I recall. Pretty important especially at lower levels to keep in mind. Even at end-game play applying mage armor copiously to one's buddies adding a 4 point increase to touch AC against dread wraiths adds up PDQ.