A time-honored maximum of computer security has been that you don't have a secure system unless you can provide a level of physical security for all of the hardware in the computer system. Some secure military computing sites go as far as not only providing as secure building to house the computing hardware, but also to provide electronic shielding to contain any electro magnetic radiation which may be generated by the computing system.
Unfortunately, when the Internet is used in computing applications, it is not practical to secure, physically, all elements of the computing system, nor is it always possible to provide physical verification of the identity of a remote computer system user. Since physical security is not possible on Internet based systems, the inherent risks must be assessed and be compared with the benefits to be derived from using Internet technology in the system design.