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414 Chapter 6 • Infrastructure Security: Devices and Media

Summary of Exam Objectives

For the Security+ exam, it is important to know and understand many different
aspects of devices and media. In the area of devices, it is necessary to understand
the three major types of firewalls and how they function.

■ Packet filtering firewalls block packets based on the IP address and port.

■ Application-layer gateways allow a greater level of security by examining
each packet to verify that it has the correct content of the communication
session that it is attempting to use.

■ Stateful inspection firewalls are a compromise between these two tech-
nologies.They have speed close to that of packet filtering, with a higher
security level.They verify that each packet going through the firewall
belongs to a valid communications session.

Routers basically shuttle packets between their interfaces, each of which is
attached to a different subnet.A router examines the destination of the packet and
sends the packet out the appropriate interface belonging to the packet’s destination
network.
A switch is a device that allows for fast, reliable communication within a
subnet.They can also support packet switching over multiple subnets by using
VLANs.A switch makes a direct connection between devices communicating to
each other through its ports.This eliminates collisions that are common with hubs
and also limits the amount of data that can be obtained by packet sniffing on one
of the switch’s ports.
Wireless technology allows network communication to take place without any
wires connecting it to the network.This technology is useful but brings security
risks with it. Securing a wireless access point is critical to making sure that the
wireless network is secure.This device also allows administrators to implement
encryption over their wireless network that will help a great deal with security.
Modems allow a backdoor into many otherwise secure networks. In many
environments, either servers or users’ systems have modems in them that can allow
intruders to dial into a computer that is also located on the network.Through this
medium, they can gain remote access to the network while completely bypassing
the firewalls.
RAS is a method of providing remote access to corporate network users who
travel or who need to access the network from home.Typically, a bank of modems
is connected to the RAS system into which users can dial and provide authentica-

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