A system and related method for determining whether an electrical circuit has been compromised. The system includes a circuit probe positioned relative to the electrical circuit that detects electromagnetic circuit emissions therefrom and an analysis device electrically coupled to the circuit probe and receiving electromagnetic emissions detection signals therefrom, where the analysis device identifies constituent frequencies and their magnitudes in the detection signals. The system also includes a comparison processor responsive to the constituent frequencies and magnitudes from the analysis device, where the comparison processor compares the constituent frequencies and magnitudes to previously stored constituent frequencies and magnitudes obtained from an equivalent test circuit to the electrical circuit to determine whether the electrical circuit has been compromised. A background probe can be provided to obtain background emissions that can be subtracted from the circuit emissions.