What do you call the process by which an electrical current is used to neutralize the magnetic field around a ship’s hull in order to avoid detection by magnetic sensors?

The ship’s hull which is made of steel acts like a large floating magnet surrounded by an even larger magnetic field.         This result to a distortion on the Earth’s magnetic field and the ship can therefore act as a trigger device for magnetic sensitive devices which are designed to detect these distortions. So to reduce the effect of the ship on the Earth’s magnetic field, a degaussing system is installed aboard.