Abstract: An exterior security gate for preventing passage through a passageway includes a grate structure shaped and dimensioned to fit over and cover the passageway. The grate structure includes a first side frame member and a second side frame member. A first hinge is secured to the first side frame member for pivotally mounting the grate structure to an exterior wall of a building structure. A chain with a plurality of apertures is secured to and extends from the second side frame member. The chain is of a length sufficient to pass through a bore formed in the building structure in the area proximate to the passageway with the grate structure positioned over the passageway. A tamper shield bracket is secured along an interior wall of the building structure in alignment with the bore. The tamper shield bracket includes a locking pin selectively positioned within an aperture of the chain to securely lock the grate structure in a closed orientation.