11.10. Physical Emissions
Although it's really outside the scope of this book, it's
important to remember that computing and communications equipment leaks a lot
information that makes them hard to really secure.
Many people are aware of TEMPEST requirements which deal with
radio frequency emissions of computers, displays, keyboards, and other
components which can be eavesdropped.
The light from displays can also be eavesdropped, even if it's bounced off an
office wall at great distance
[Kuhn 2002].
Modem lights are also enough to determine the underlying communication.