An armored resistor (1) comprising a tubular casing (2) in which a metallic heating element (3) immersed in an electrically insulating material (4) is arranged. Furthermore, a first closing element (5) and a second closing element (6) of the tubular casing (2) are provided, in which the first closing element (5) is fluid-tightly fixed to the respective first end (7) of the tubular casing (2), and the second closing element (6) is provided with at least one at least one radial protrusion (15) which abuts on the second end (8) of the tubular casing (2), and which delimits at least one passage (16) communicating with the inside of the tubular casing (2), adapted to allow the passage of the electrically insulating material during the manufacturing of the armored resistor.