Spoofer
From Halopedia, the Halo wiki
The spoofer is used by the UNSC forces to force open doors and override certain pieces of equipment that may be locked, damaged, or otherwise unable to function.
They are standard equipment to Marine fire teams when deployed into ground engagements. One was used to open the door in the containment facility where the Flood were released from.[1]
Private Kappus used one to open the door to the Flood Containment Facilities. He was ordered by Captain Keyes to open the door that happened to be the only thing holding back the Flood. Unwillingly and unknowingly, Kappus unleashed the Flood on Installation 04, dooming him and the rest of his squad,[2] save for Johnson. When an Infection Form attached itself to Kappus' friend Riley, he got it off successfully. Kappus was soon transformed into a Combat Form, though.
