Protection against attacks on integrated circuits using voltage monitoring

An Integrated Circuit (IC) includes functional circuitry and attack-protection circuitry (APC). The functional circuitry is to receive a supply voltage from a power-supply input. The APC is coupled to the power-supply input and includes a front-end circuit and an averaging circuit. The front-end circuit is to compare the supply voltage to a plurality of voltage thresholds, and to output a respective plurality of indications that indicate whether the supply voltage violates the respective voltage thresholds. The averaging circuit is to estimate, for a selected subset of the indications, respective duty-cycles at which the indications in the subset exceed the respective voltage thresholds. The APC is to trigger one or more attack detection events in response to the indications and the duty-cycles.