Abstract: A security cover lockably engageable with surface mounted apparatus for preventing unauthorized access to the apparatus. The security cover includes a shell with peripheral sides which closely conform to the size of the apparatus over which it fits, and a pair of tangs on the shell edge wedgable between the apparatus and the surface. A key lock is mounted within the outer surface of the protective cover and includes a slotted finger rotatable with the lock cylinder. The fastener with which the apparatus is fixed to the surface is replaced by a double-headed fastener and is engageable with the slotted finger to thereby lock the protective cover to the apparatus. In the alternative, another apparatus screw is replaced with a double-headed fastener and, instead of tangs, a side edge of the cover is slotted for engagement with the second double-headed screw.