Wireless Security.pdf - PDF Archive

704 Appendix B
device that is configured to use DHCP contacts the DHCP server to request an IP address.
The DHCP server then assigns an IP address from the range it has been configured to
use. The IP address is leased for a certain amount of time. When the device is removed
from the network or when the lease expires, the IP address is placed back into the pool
to be used by another device.
Demilitarized Zone: The demilitarized zone (DMZ) is a neutral zone or buffer that
separates the internal and external networks and usually exists between two firewalls.
External users can access servers in the DMZ, but not the computers on the internal network.
The servers in the DMZ act as an intermediary for both incoming and outgoing traffic.
DNS: The Domain Name System (DNS) was created to provide a way to translate
domain names to their corresponding IP addresses. It is easier for users to remember
a domain name (e.g., yahoo.com) than to try and remember an actual IP address (e.g.,
65.37.128.56) of each site they want to visit. The DNS server maintains a list of domain
names and IP addresses so that when a request comes in it can be pointed to the correct
corresponding IP address.
Keeping a single database of all domain names and IP addresses in the world would be
exceptionally difficult, if not impossible. For this reason, the burden has been spread
around the world. Companies, Web hosts, ISPs, and other entities that choose to do so can
maintain their own DNS servers. Spreading the workload like this speeds up the process
and provides better security instead of relying on a single source.
Denial of Service: A Denial-of-Service (DoS) attack floods a network with an
overwhelming amount of traffic, thereby slowing its response time for legitimate traffic or
grinding it to a halt completely. The more common attacks use the built-in features of the
Transmission Control Protocol (TCP)/IP to create exponential amounts of network traffic.
E-mail Spoofing: E-mail spoofing is the act of forging the header information on an
e-mail so that it appears to have originated from somewhere other than its true source.
The protocol used for e-mail, Simple Mail Transfer Protocol (SMTP), does not have any
authentication to verify the source. By changing the header information, the e-mail can
appear to come from someone else.
E-mail spoofing is used by virus authors. By propagating a virus with a spoofed e-mail
source, it is more difficult for users who receive the virus to track its source. E-mail
spoofing is also used by distributors of spam to hide their identity.
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