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Technology in Action
Chapter 7
Networking and Security:
Connecting Computers and Keeping
Them Safe from Hackers and Viruses
© 2009 Prentice-Hall, Inc.
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Chapter Topics
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Networking fundamentals
Network architecture
Network components
Peer-to-peer networks
Ethernet networks
Computer threats
Computer safeguards
Computer viruses
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Networking Fundamentals
• Computer network:
– Two or more computers connected together
– Devices connected to networks: nodes
• Benefits of a network:
– Sharing resources
– Transferring files
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Network Architecture
• Network designs:
– Locally administered:
• Peer-to-peer (P2P)
– Centrally administered:
• Client/server
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Peer-to-Peer Networks
• Nodes communicate
with each other:
– Peers
• Share peripheral
devices
• Used in home and
small office networks
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Client/Server Networks
• Client computers:
– Users who make
requests
• Server computers:
– Provide resources to
clients
– Central network control
• Internet
– A large, multiserver,
multiclient network.
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LANs and WANs
• Local area network (LAN):
– Nodes are within a small geographic region:
• Homes
• Schools
• Small businesses
• Wide area network (WAN):
– LANs connected over long distances:
• A few miles to thousands of miles
• Use telecommunications lines
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Network Components
• Transmission media
• Network communication
devices
• Software
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Transmission Media
• Provides communications channel between
nodes
• Forms of media:
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Twisted pair
Coaxial cable
Fiber-optic cable
Radio waves:
• Wireless
• Bandwidth:
– Data transfer rate
– Throughput
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Network Adapters
• Devices connected to or installed in nodes:
– Network interface cards (NICs)
– External network adapters
• Enable communication between nodes
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Network Navigation Devices
• Devices that help make data flow possible
• Routers:
– Route data between networks
• Switches:
– Receive data and retransmit it to nodes on the
same network
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Networking Software
• Peer-to-Peer Software
• Built into operating systems that support
networking
– Windows
– Mac OS
• Client/Server Software
• Network operating system (NOS) software
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Windows XP Professional
Windows Server 2003
Novell Netware
Windows Vista Enterprise
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Types of Peer-to-Peer Networks
• Wired Ethernet networks
• Wireless Ethernet networks
• Power-line networks
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Wired Ethernet Networks
• Ethernet network
adapters are used to
connect nodes
– NIC card
– PC Card
– USB adapter
• Computers are
connected to each
other using unshielded
twisted pair cable
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Ethernet
Phone
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Ethernet Switches
• Keep track of data packets
• Amplify and retransmit signals
• Keep the network running efficiently
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Ethernet Routers
• Transfer packets from one network to another
• Home Internet routers transfer data from the
Internet to the home network.
Router
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Wireless Ethernet Networks
• Uses radio waves to connect nodes
• Basically an Ethernet network that uses radio
waves instead of wires
• Each node requires a wireless network adapter:
– Transceivers
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Power-Line Networks
• Computers are
connected to a
house’s electrical
wiring to create a
network
• Power-line network
adapter is used to
connect nodes to
electrical outlets
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Choosing a Peer-to-Peer
Network
• Things to consider:
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Whether you want wireless communications
How fast you want your network connection to be
Whether existing wiring is available
How much money you can spend on your network
Comparing the Major Types of Home Networks
Wired
Ethernet
Wireless
802.11g
Wireless
Enhanced G
Wireless
802.11n
Maximum data
Transfer rate
(bandwidth)
100 Mbps to
1,000 bps
(1 gigabit)
54 Mbps
108 Mbps
100 to 630 bps
Relative installation
and equipment costs
for networking
two computers
$
$
$$
$$$
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Configuring Software
for a Home Network
• Windows
– Windows Vista home versions
• Network setup wizard
– Wired or wireless
– Windows XP
• Network setup wizard
– Windows 98
• Configure manually
– Help has a clear instruction
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Computer Threats
• Cybercrimes are criminal acts conducted through
the use of computers by cybercriminals.
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Hackers
• Anyone who unlawfully accesses a
computer system
• Types of hackers:
– White-hat
– Black-hat
– Script kiddies
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What Hackers Do
• Steal information from computers:
– Credit card numbers
– Bank account numbers
• Internet packet sniffing
• Commit identity theft
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How Computers Are Attacked
• Trojan horse
• Backdoor
program
– Zombies
• Denial of
service attacks
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How Hackers Gain Access
• Direct access:
– Hacking software
• Indirect access:
– Internet connection
– Logical ports
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Computer Safeguards:
Firewalls
• Software programs or hardware designed
to close logical ports to invaders
– A firewall is built into Windows Vista
– More robust firewalls are available from
other vendors
– Firewalls are critical if you have an alwayson broadband connection
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Protecting a Wireless Network
• Wireless network range doesn’t stop at the
property line
• Default device and network ID settings
allow intruders to enter the network
• Internet bandwidth can be stolen
• Computers can be vulnerable to hacker
intrusion and takeover
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Computer Threats: Viruses
• A program that attaches itself to another
program and spreads itself to other
computers
• Viruses are hidden within the code of a
host program
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How Does a Computer
Catch a Virus?
• Viruses copy
themselves
• Infect a file on
your computer
• Spread by sharing
disks or flash
drives
• E-mail
attachments are
the most likely
source of a virus
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What Viruses Do
• Replicate themselves:
– Slow down networks
• Secondary objectives:
– Display annoying messages
– Delete files on the hard drive
– Change computer settings
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Types of Viruses
• Boot-sector viruses
– Replicate themselves in the boot sector of the hard
drive
• Logic bombs
– Activate when certain conditions are met
• Time bombs
– Viruses that are triggered by the passage of time or
on a certain date
• Worms
– Travel between systems through networks
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Types of Viruses
• Script viruses:
– Hidden on Web pages as mini programs
• Macro viruses:
– Attached to documents
– Series of commands
• E-mail virus
– Use e-mail address book to distribute the virus
• Encryption viruses
– Compresses files using a complex encryption key
– User must pay to get the files unlocked
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Virus Classifications
• Polymorphic viruses:
– Periodically rewrite themselves to avoid
detection
• Multipartite viruses:
– Infect multiple file types
• Stealth viruses:
– Erase their code from the hard drive and
reside in the active memory
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Antivirus Software
• Programs designed to detect viruses:
– Scan files looking for virus signatures (unique code)
– Provide options for deleting or fixing infected files
– Inoculate files against further infection
• Detect known viruses
• Antivirus programs need to be updated frequently
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Chapter 7 Summary Questions
• What is a network, and what are the
advantages of setting up one?
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Chapter 7 Summary Questions
• What is the difference between a
client/server network and a peer-to-peer
network?
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Chapter 7 Summary Questions
• What are the main components of every
network?
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Chapter 7 Summary Questions
• What are the most common home
networks?
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Chapter 7 Summary Questions
• What are wired Ethernet networks, and
how are they created?
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Chapter 7 Summary Questions
• What are wireless Ethernet networks, and
how are they created?
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Chapter 7 Summary Questions
• How are power-line networks created, and
are they viable alternatives to Ethernet
networks?
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Chapter 7 Summary Questions
• How can hackers attack a network, and
what harm can they cause?
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Chapter 7 Summary Questions
• What is a firewall, and how does it keep
my computer safe from hackers?
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Chapter 7 Summary Questions
• Why are wireless networks more
vulnerable than wired networks, and what
special precautions are required to ensure
my wireless network is secure?
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Chapter 7 Summary Questions
• From which types of viruses do I need to
protect my computer?
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Chapter 7 Summary Questions
• What can I do to protect my computer from
viruses?
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