Another possible brute force eeprom attack, applicable to many semiconductor chips, is applying an external high voltage signal (normally twice the power supply) to the chip’s eeprom pins to find out whether one of them has any transaction like entering into a factory test or programming mode. In fact, such pins can be easily found with a digital multimeter because they do not have a protection diode to the power supply line. Once sensitivity to a high voltage is found for any pin, the eeprom  attacker can try a systematic search on possible combinations of logic signals applied to other pins to figure out which of them are used for the test/programming mode and exploit this opportunity.

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