Samus encounters this rogue security robot twice while she is exploring the BSL research station. The first time is in sector 3 (PYR). At that point it had just gone rogue, but was otherwise normal. After Samus had damaged its outer casing in that fight, it became vulnerable to infection by the X, who promptly took up residence in its neural network. Her second encounter with this strengthened machine took place in sector 6 (NOC),and was made more difficult due to it having upgraded weapons systems.
During the first fight, it deploys bombs
that create pillars of fire, which can be avoided by positioning Samus directly over them, and then she can put shots on the armored core of the robot. During the second fight, it fires homing rockets
at Samus, and it is able to jump high enough to knock her down into the electrified water below. After it is sufficiently damaged, the Core-X
emerges and Samus must fight it. After it is defeated, she recieves the Wave Beam