Page 775 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

credit card numbers, IP addresses, system names, and so on.

Packet sniffing and other attacks are discussed in more detail in
Chapter 13.

Domain Name System

Addressing and naming are important components that make network
communications possible. Without addressing schemes, networked
computers would not be able to distinguish one computer from
another or specify the destination of a communication. Likewise,
without naming schemes, humans would have to remember and rely
on numbering systems to identify computers. It is much easier to

remember Google.com than 64.233.187.99. Thus, most naming
schemes were enacted for human use rather than computer use.

It is reasonably important to grasp the basic ideas of addressing and
numbering as used on TCP/IP-based networks. There are three
different layers to be aware of. They’re presented in reverse order here
because the third layer is the most basic:

The third, or bottom, layer is the MAC address. The MAC address,

or hardware address, is a “permanent” physical address.

The second, or middle, layer is the IP address. The IP address is a
“temporary” logical address assigned over or onto the MAC
address.

The top layer is the domain name. The domain name or computer
name is a “temporary” human-friendly convention assigned over or
onto the IP address.

“Permanent” and “Temporary” Addresses

The reason these two adjectives are within quotation marks is that
they are not completely accurate. MAC addresses are designed to
be permanent physical addresses. However, some NICs support

MAC address changes, and most modern operating systems
(including Windows and Linux) do as well. When the NIC supports