Conventional IT systems cannot be fully protected from external attack. In contrast, HSMs feature a whole array of protective mechanisms to deter physical tampering, typically including drill protection foil, resin-embedded chips as well as temperature and voltage sensors. If, for instance, someone should attempt to open an HSM e.g. by drilling into the device, eroding layers by applying acid or icing up and breaking open the casing, sensors will register such an attack immediately, triggering an alarm. Additionally, special applications installed on the HSM automatically initiate countermeasures as specified by the configuration, e.g. deletion of keys.
In this way, HSMs offer maximum security from external physical, chemical or mechanical attack. In fact, there are currently no practically workable attacks that would be able to overcome all these physical protection features.