Attack MCU Firmware is actually a process of decapsulate the silicon package of microcontroller and disable its fuse bit by focus ion beam, then extract code from MCU flash memory;
All microprobing and reverse engineering microcontroller techniques are invasive mcu firmware attacks. They require hours or weeks in specialised laboratory and in the process they destroy the packaging.
The other three are non-invasive mcu cracking methods. The microprocessor code extracting device is not physically harmed during these ic cracks. The last MCU breaking category could also be semi-invasive. It means that the access to the chip’s die is required but the attack is not penetrative and the fault is generated with intensive light pulse, radiation, local heating or other means.