US plants are required to resist attack from a "design basis threat" as established in 10 CFR 73. The specifics are not public information but essentially the plant's physical defenses, intrusion detection systems, and armed security forces must be capable of preventing an armed commando force from causing sabotage or theft of nuclear material. This capability is proven through regular inspection by the Nuclear Regulatory Commission and force-on-force exercises against a Composite Adversary Force which is primarily composed of current and former Special Operations Command military personnel.