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
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.