What are the four classes of physical threats to network security?
Hardware, environmental, electrical, and maintenance threats.
Network security is not only about software — if an attacker (or simply bad housekeeping) can physically reach the equipment, all the logical controls in the world won't help. The four classes group the physical risks so a secure equipment room can be designed to address each one:
-
Hardware threats - Physical damage to servers, routers, switches, cabling, and workstations, whether deliberate (theft, sabotage) or accidental.
-
Environmental threats - Temperature extremes (too hot or too cold) or humidity extremes (too wet or too dry), which cause equipment to overheat or corrode.
-
Electrical threats - Voltage spikes, brownouts (insufficient supply voltage), unconditioned power (electrical noise), and total power loss — mitigated with UPS units and surge protection.
-
Maintenance threats - Poor handling of components (e.g. electrostatic discharge, ESD), lack of critical spare parts, and poor cabling and labelling that makes safe servicing hard.
Go deeper:
Computer security — Wikipedia — its "physical access attacks" section explains why logical controls fail once an attacker can reach the hardware.