Physical security matters. Your data is just as gone if somebody wipes your computer's disks during a break-in or melts your computer's disks by setting fire to your machine room. Fortunately, physical threats to information systems are among the easiest to understand and the cheapest to defend against.
It may seem that the advice in this chapter is a hodge-podge of common sense. In fact, we have tried hard to give you a solid approach for understanding and characterizing the many physical threats that may befall your computer systems.
Physical security is hard because some of the threats that you are protecting against are natural, while others are man-made. A good security policy protects against both sets of risks.