Methods of detecting unwanted logic in an integrated circuit (IC) design. Any unwanted logic added to a design (e.g., to monitor or interfere with operation of the design) will draw power from one or more power supplies on the IC. Hence, by monitoring power drawn from various portions of a circuit design implemented in an IC, the unwanted logic can be detected and reported to the user. One way of monitoring power draw is by the use of oscillator circuits. If power goes down locally (e.g., due to the operation of unwanted logic), the frequency of an oscillator circuit in that vicinity will be reduced relative to the frequencies of other oscillator circuits in the design, and/or relative to an expected value. When a variation in the relative power consumption is detected, unwanted logic can be inferred and an error signal is output.